FW Pos C: move setting of control_mode_current to separate function and minor clean ups

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

src/modules/fw_pos_control_l1/FixedwingPositionControl.hpp

@@ -344,6 +344,7 @@ private:
 	void		reset_takeoff_state(bool force = false);
 	void		reset_landing_state();
 	Vector2f 	get_nav_speed_2d(const Vector2f &ground_speed);
+	void		set_control_mode_current(bool pos_sp_curr_valid);
 
 	/*
 	 * Call TECS : a wrapper function to call the TECS implementation