AP_InertialSensor: compile warnings: format not a string literal, argument types not checked

PSTR() goofs things up when using hal.console->printf_P()

libraries/AP_InertialSensor/AP_InertialSensor_MPU6000.cpp

@@ -450,7 +450,7 @@ void AP_InertialSensor_MPU6000::_register_write_check(uint8_t reg, uint8_t val)
     _register_write(reg, val);
     readed = _register_read(reg);
     if (readed != val){
-	hal.console->printf_P(PSTR("Values doesn't match; written: %02x; read: %02x "), val, readed);
+	hal.console->printf_P("Values doesn't match; written: %02x; read: %02x ", val, readed);
     }
 #if MPU6000_DEBUG
     hal.console->printf_P(PSTR("Values written: %02x; readed: %02x "), val, readed);