HAL_ChibiOS: disable loop() delay for iofirmware

libraries/AP_HAL_ChibiOS/HAL_ChibiOS_Class.cpp

@@ -208,9 +208,11 @@ static void main_loop()
           time from the main loop, so we don't need to do it again
           here
          */
+#ifndef HAL_DISABLE_LOOP_DELAY
         if (!schedulerInstance.check_called_boost()) {
             hal.scheduler->delay_microseconds(250);
         }
+#endif
     }
     thread_running = false;
 }

libraries/AP_HAL_ChibiOS/hwdef/iomcu/hwdef.dat

@@ -121,3 +121,4 @@ define NO_FASTBOOT
 IOMCU_FW 1
 MAIN_STACK 0x200
 PROCESS_STACK 0x250
+define HAL_DISABLE_LOOP_DELAY