Refactor pixel rain animation

Remove redundant params pointer

Use informative led_index variable

Place random on/off boolean within "if" statement

quantum/rgb_matrix/animations/pixel_rain_anim.h

@@ -12,23 +12,23 @@ static bool PIXEL_RAIN(effect_params_t* params) {
         return 500 / scale16by8(qadd8(rgb_matrix_config.speed, 16), 16);
     }
 
-    void rain_pixel(uint8_t i, effect_params_t * params, bool off) {
-        if (!HAS_ANY_FLAGS(g_led_config.flags[i], params->flags)) {
+    inline void rain_pixel(uint8_t led_index) {
+        if (!HAS_ANY_FLAGS(g_led_config.flags[led_index], params->flags)) {
             return;
         }
-        if (off) {
-            rgb_matrix_set_color(i, 0, 0, 0);
+        if (random8() & 2) {
+            rgb_matrix_set_color(led_index, 0, 0, 0);
         } else {
             HSV hsv = {random8(), random8_min_max(127, 255), rgb_matrix_config.hsv.v};
             RGB rgb = rgb_matrix_hsv_to_rgb(hsv);
-            rgb_matrix_set_color(i, rgb.r, rgb.g, rgb.b);
+            rgb_matrix_set_color(led_index, rgb.r, rgb.g, rgb.b);
         }
         wait_timer = g_rgb_timer + interval();
     }
 
     RGB_MATRIX_USE_LIMITS(led_min, led_max);
     if (g_rgb_timer > wait_timer) {
-        rain_pixel(random8_max(RGB_MATRIX_LED_COUNT), params, random8() & 2);
+        rain_pixel(random8_max(RGB_MATRIX_LED_COUNT));
     }
     return rgb_matrix_check_finished_leds(led_max);
 }