AP_InertialSensor: fixed setup of DRDY pin on MPU9250

libraries/AP_InertialSensor/AP_InertialSensor_MPU9250.cpp

@@ -206,8 +206,7 @@ uint16_t AP_InertialSensor_MPU9250::_init_sensor( Sample_rate sample_rate )
     _spi = hal.spi->device(AP_HAL::SPIDevice_MPU9250);
     _spi_sem = _spi->get_semaphore();
     _drdy_pin = hal.gpio->channel(BBB_P8_7);
-    // For some reason configuring the pin as an input make the driver fail
-    // _drdy_pin->mode(GPIO_IN);
+    _drdy_pin->mode(HAL_GPIO_INPUT);
 
     hal.scheduler->suspend_timer_procs();