Potentially infinite and deleted loops found by PVS-Studio (#7100)

 - Fixed V712
 - The compiler can optimize this code by creating an infinite loop, or simply deleting it.
 - There is need to add a volatile qualifier to the '_ExitFlag' and 'sim_delay' variables.

src/drivers/device/vdev_posix.cpp

@@ -55,7 +55,7 @@ using namespace device;
 pthread_mutex_t filemutex = PTHREAD_MUTEX_INITIALIZER;
 px4_sem_t lockstep_sem;
 bool sim_lockstep = false;
-bool sim_delay = false;
+volatile bool sim_delay = false;
 
 extern "C" {
 

src/platforms/posix/main.cpp

@@ -71,7 +71,7 @@ const unsigned path_max_len = PATH_MAX;
 const unsigned path_max_len = 1024;
 #endif
 
-static bool _ExitFlag = false;
+static volatile bool _ExitFlag = false;
 
 static struct termios orig_term;