mavlink: remove implicit cast from int to bool

It confused me that we used an int result and casted it into a boolean.

This doesn't change the logic but makes handling the return value explicit.

src/modules/mavlink/mavlink_mission.cpp

@@ -305,18 +305,18 @@ void
 MavlinkMissionManager::send_mission_item(uint8_t sysid, uint8_t compid, uint16_t seq)
 {
 	mission_item_s mission_item = {};
-	bool read_success = false;
+	int read_result = 0;
 
 	switch (_mission_type) {
 
 	case MAV_MISSION_TYPE_MISSION: {
-			read_success = dm_read(_dataman_id, seq, &mission_item, sizeof(mission_item_s)) == sizeof(mission_item_s);
+			read_result = dm_read(_dataman_id, seq, &mission_item, sizeof(mission_item_s)) == sizeof(mission_item_s);
 		}
 		break;
 
 	case MAV_MISSION_TYPE_FENCE: { // Read a geofence point
 			mission_fence_point_s mission_fence_point;
-			read_success = dm_read(DM_KEY_FENCE_POINTS, seq + 1, &mission_fence_point, sizeof(mission_fence_point_s)) ==
+			read_result = dm_read(DM_KEY_FENCE_POINTS, seq + 1, &mission_fence_point, sizeof(mission_fence_point_s)) ==
 				      sizeof(mission_fence_point_s);
 
 			mission_item.nav_cmd = mission_fence_point.nav_cmd;
@@ -337,7 +337,7 @@ MavlinkMissionManager::send_mission_item(uint8_t sysid, uint8_t compid, uint16_t
 
 	case MAV_MISSION_TYPE_RALLY: { // Read a safe point / rally point
 			mission_safe_point_s mission_safe_point;
-			read_success = dm_read(DM_KEY_SAFE_POINTS, seq + 1, &mission_safe_point, sizeof(mission_safe_point_s)) ==
+			read_result = dm_read(DM_KEY_SAFE_POINTS, seq + 1, &mission_safe_point, sizeof(mission_safe_point_s)) ==
 				      sizeof(mission_safe_point_s);
 
 			mission_item.nav_cmd = MAV_CMD_NAV_RALLY_POINT;
@@ -353,7 +353,7 @@ MavlinkMissionManager::send_mission_item(uint8_t sysid, uint8_t compid, uint16_t
 		break;
 	}
 
-	if (read_success) {
+	if (read_result > 0) {
 		_time_last_sent = hrt_absolute_time();
 
 		if (_int_mode) {