pybricks/util_pb/pb_imu: flip Prime Hub IMU

Based on its output values, it appears that the Technic Hub and Prime Hub have this sensor on opposite sides of the PCB.

While orientation is configurable, it is helpful that the default orientation is the same at the driver level, with the buttons facing up.

pybricks/util_pb/pb_imu.c

@@ -183,6 +183,12 @@ void pb_imu_accel_read(pb_imu_dev_t *imu_dev, float_t *values) {
     values[0] = data[0] * imu_dev->accel_scale;
     values[1] = data[1] * imu_dev->accel_scale;
     values[2] = data[2] * imu_dev->accel_scale;
+
+    #if PYBRICKS_HUB_PRIMEHUB
+    // Sensor is upside down
+    values[0] = -values[0];
+    values[2] = -values[2];
+    #endif
 }
 
 void pb_imu_gyro_read(pb_imu_dev_t *imu_dev, float_t *values) {
@@ -203,6 +209,12 @@ void pb_imu_gyro_read(pb_imu_dev_t *imu_dev, float_t *values) {
     values[0] = data[0] * imu_dev->gyro_scale;
     values[1] = data[1] * imu_dev->gyro_scale;
     values[2] = data[2] * imu_dev->gyro_scale;
+
+    #if PYBRICKS_HUB_PRIMEHUB
+    // Sensor is upside down
+    values[0] = -values[0];
+    values[2] = -values[2];
+    #endif
 }
 
 #endif // PYBRICKS_PY_COMMON && PYBRICKS_PY_COMMON_IMU