use consistent orientation naming in messages

src/modules/commander/accelerometer_calibration.cpp

@@ -263,7 +263,7 @@ int do_accel_calibration_measurements(int mavlink_fd, float accel_offs[3], float
 	const int samples_num = 2500;
 	float accel_ref[6][3];
 	bool data_collected[6] = { false, false, false, false, false, false };
-	const char *orientation_strs[6] = { "front", "back", "left", "right", "top", "bottom" };
+	const char *orientation_strs[6] = { "front", "back", "left", "right", "up", "down" };
 
 	int sensor_combined_sub = orb_subscribe(ORB_ID(sensor_combined));