Mantis: add comment about boot order.

The boot order is now:
1. The PX4 bootloader boots, and starts the camera.
2. The camera starts and sends the boot command to the PX4 bootloader.
3. PX4 starts.

boards/atl/mantis-edu/src/init.c

@@ -114,6 +114,8 @@ static void cam_pwr_on_pulse(void)
 	static bool pwr_on_flag = false;
 
 	if (pwr_on_flag == false) {
+		// This is now done in the bootloader.
+		// However, for transition we can leave it in.
 		up_mdelay(700);
 		stm32_configgpio(GPIO_CAM_PWR_ON_H);
 		up_mdelay(20);