feat(m5stack): sharing SPI bus with an SD card

The [m5stack][1] development boards share the same SPI bus
bewtween their display (ili9341) and SD card interface. This leads
to an SPI bus conflict when trying to use the display and SD card
simultaneously, as previously reported by [others][2] using
the same display. This commit intruduces 2 new build flags
that modify the compilation of the modILI9341.c module:

`LV_M5STACK`: When defined, adjust the screen rotation and color
              mapping to match the M5Stack modules.

`LV_ILI9341_SHARE_SPI_BUS`: When defined, assume that the SPI bus
                            has already been defined and simply add
                            the display to the existing bus. Note that
                            this also sets the display to use Full-
                            Duplex mode.

The following code provides a minimal example using LittlevGL
with an SD card interface:

```python
import machine
import os
import lvgl as lv
import lvesp32
import ILI9341

os.mount(machine.SDCard(slot=3, sck=18, mosi=23, miso=19, cs=4), '/sd')

lv.init()
disp = ILI9341.display(spihost=1, miso=19, mosi=23, clk=18, cs=14,
dc=27,
                       rst=33, backlight=32, mhz=25)
disp.init()

disp_buf1 = lv.disp_buf_t()
buf1_1 = bytearray(480*10)
lv.disp_buf_init(disp_buf1,buf1_1, None, len(buf1_1)//4)
disp_drv = lv.disp_drv_t()
lv.disp_drv_init(disp_drv)
disp_drv.buffer = disp_buf1
disp_drv.flush_cb = disp.flush
disp_drv.hor_res = 320
disp_drv.ver_res = 240
disp_drv.rotated = 0
lv.disp_drv_register(disp_drv)

scr = lv.obj()
btn = lv.btn(scr)
btn.align(lv.scr_act(), lv.ALIGN.CENTER, 0, 0)
label = lv.label(btn)
label.set_text("Button")
lv.scr_load(scr)

print(os.listdir('/sd'))
```

[1]: https://m5stack.com/collections/m5-core
[2]: https://hackaday.io/project/162059-street-sense/log/170296-farewell-loboris-hello-littlevgl

driver/esp32/modILI9341.c

@@ -150,6 +150,7 @@ STATIC void disp_spi_init(ILI9341_t *self)
 {
 	esp_err_t ret;
 
+#ifndef LV_ILI9341_SHARE_SPI_BUS
 	spi_bus_config_t buscfg={
 		.miso_io_num=self->miso,
 		.mosi_io_num=self->mosi,
@@ -158,6 +159,7 @@ STATIC void disp_spi_init(ILI9341_t *self)
 		.quadhd_io_num=-1,
 		.max_transfer_sz=128*1024,
 	};
+#endif
 
 	spi_device_interface_config_t devcfg={
 		.clock_speed_hz=self->mhz*1000*1000, //Clock out at DISP_SPI_MHZ MHz
@@ -166,10 +168,13 @@ STATIC void disp_spi_init(ILI9341_t *self)
 		.queue_size=1,
 		.pre_cb=NULL,
 		.post_cb=NULL,
+#ifndef LV_ILI9341_SHARE_SPI_BUS
 		.flags=SPI_DEVICE_HALFDUPLEX,
+#endif
 		.duty_cycle_pos=128,
 	};
 
+#ifndef LV_ILI9341_SHARE_SPI_BUS
 	gpio_pad_select_gpio(self->miso);
     gpio_pad_select_gpio(self->mosi);
     gpio_pad_select_gpio(self->clk);
@@ -185,6 +190,7 @@ STATIC void disp_spi_init(ILI9341_t *self)
 	ret=spi_bus_initialize(self->spihost, &buscfg, 1);
     if (ret != ESP_OK) nlr_raise(
         mp_obj_new_exception_msg(&mp_type_RuntimeError, "Failed initializing SPI bus"));
+#endif
 
 	//Attach the LCD to the SPI bus
 	ret=spi_bus_add_device(self->spihost, &devcfg, &self->spi);
@@ -241,7 +247,11 @@ STATIC const lcd_init_cmd_t ili_init_cmds[]={
 		{0xC1, {0x11}, 1},			/*Power control */
 		{0xC5, {0x35, 0x3E}, 2},	/*VCOM control*/
 		{0xC7, {0xBE}, 1},			/*VCOM control*/
+#ifdef LV_M5STACK
+		{0x36, {0x18}, 1},			/*Memory Access Control (COLOR_MODE_BGR | MADCTL_ML)*/ 
+#else
 		{0x36, {0x48}, 1},			/*Memory Access Control*/
+#endif
 		{0x3A, {0x55}, 1},			/*Pixel Format Set*/
 		{0xB1, {0x00, 0x1B}, 2},
 		{0xF2, {0x08}, 1},
@@ -292,6 +302,11 @@ STATIC mp_obj_t mp_init_ILI9341(mp_obj_t self_in)
 		cmd++;
 	}
 
+#ifdef LV_M5STACK
+	//Invert the display colors
+	ili9441_send_cmd(self, 0x21);
+#endif
+
 	///Enable backlight
 	//printf("Enable backlight.\n");
 	if (self->backlight != -1) gpio_set_level(self->backlight, 1);       
@@ -326,6 +341,7 @@ STATIC void ili9431_flush(struct _disp_drv_t * disp_drv, const lv_area_t * area,
 
 	uint32_t size = (area->x2 - area->x1 + 1) * (area->y2 - area->y1 + 1);
 
+#ifndef LV_M5STACK
 	/*Byte swapping is required*/
 	uint32_t i;
 	uint8_t * color_u8 = (uint8_t *) color_p;
@@ -335,6 +351,7 @@ STATIC void ili9431_flush(struct _disp_drv_t * disp_drv, const lv_area_t * area,
 		color_u8[i + 1] = color_u8[i];
 		color_u8[i] = color_tmp;
 	}
+#endif
 
 	ili9341_send_data(self, (void*)color_p, size * 2);