param: Move to POSIX semaphore abstraction

src/modules/systemlib/param/param.c

@@ -147,14 +147,14 @@ static param_t param_find_internal(const char *name, bool notification);
 static void
 param_lock(void)
 {
-	//do {} while (sem_wait(&param_sem) != 0);
+	//do {} while (px4_sem_wait(&param_sem) != 0);
 }
 
 /** unlock the parameter store */
 static void
 param_unlock(void)
 {
-	//sem_post(&param_sem);
+	//px4_sem_post(&param_sem);
 }
 
 /** assert that the parameter store is locked */