Fixes for posix-arm and qurt builds

Ifdefed out deadcode in position_estimator_inav_main.c as the
deadcode does not compile for qurt.

Added fixes to get a successful build for posix-arm and qurt targets.
Removed CLOCK_REALTIME def from px4_time.h for qurt and removed unused
variables in att_est_q and mc_att_control.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/simulator/simulator.h

@@ -210,8 +210,9 @@ private:
 	_baro_pub(nullptr),
 	_gyro_pub(nullptr),
 	_mag_pub(nullptr),
-	_initialized(false),
+	_initialized(false)
 #ifndef __PX4_QURT
+	,
 	_rc_channels_pub(nullptr),
 	_actuator_outputs_sub(-1),
 	_vehicle_attitude_sub(-1),