px4fmu-v4: Fix for HIL Unable to Set Control Surfaces. Fixes #5651

The sensor_rest command added to the startup script for px4fmu_v4 hardware
was leaving the /dev/pwm_output0 driver open.  This would prevent the
pwm_out_sim module from registering as a simulated driver.  The result
would cause the system to properly boot in HIL mode, but you would not
be able to set any control surfaces.

Since sensor_rest and peripheral_reset are only used on initialization, the
drivers can be shut down after they have performed their reset functions.

Signed-off-by: zthorson <zachthorson@gmail.com>

src/drivers/px4fmu/fmu.cpp

@@ -3396,6 +3396,10 @@ fmu_main(int argc, char *argv[])
 			warnx("resettet default time");
 		}
 
+		// When we are done resetting, we should clean up the fmu drivers
+		// Failure to do so prevents other devices (HIL sim driver)
+		// from starting.
+		fmu_stop();
 		exit(0);
 	}
 
@@ -3409,6 +3413,10 @@ fmu_main(int argc, char *argv[])
 			warnx("resettet default time");
 		}
 
+		// When we are done resetting, we should clean up the fmu drivers
+		// Failure to do so prevents other devices (HIL sim driver)
+		// from starting.
+		fmu_stop();
 		exit(0);
 	}