AP_OpticalFlow: support ChibiOS

libraries/AP_OpticalFlow/OpticalFlow.cpp

@@ -89,7 +89,7 @@ void OpticalFlow::init(void)
     }
 
     if (!backend) {
-#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
+#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN || defined(HAL_CHIBIOS_ARCH_FMUV3)
         if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_PIXHAWK) {
             // possibly have pixhart on external SPI
             backend = AP_OpticalFlow_Pixart::detect(*this);
@@ -104,6 +104,8 @@ void OpticalFlow::init(void)
         backend = new AP_OpticalFlow_Onboard(*this);
 #elif CONFIG_HAL_BOARD == HAL_BOARD_LINUX
         backend = AP_OpticalFlow_PX4Flow::detect(*this);
+#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_CHIBIOS_SKYVIPER_F412
+        backend = AP_OpticalFlow_Pixart::detect(*this);
 #endif
     }