rocr: Fix Potential Deadlock

Because eventDescrp->mutex is a non-recursive lock attempting to
acquire the lock with pthread_mutex_lock can cause the system to hang
indefinitely if the lock was already previously aquired with the
preceeding call to pthread_mutex_trylock.

Signed-off-by: Sunday Clement <Sunday.Clement@amd.com>

runtime/hsa-runtime/core/util/lnx/os_linux.cpp

@@ -577,7 +577,10 @@ int WaitForOsEvent(EventHandle event, unsigned int milli_seconds) {
   }
 
   int ret_code = 0;
-  pthread_mutex_lock(&eventDescrp->mutex);
+  if(milli_seconds != 0) {
+    pthread_mutex_lock(&eventDescrp->mutex);
+  }
+  
   if (!eventDescrp->state) {
     if (milli_seconds == 0) {
       ret_code = 1;