[OpenACC] Missing unlocking on error paths in attach/detach code, part II

	libgomp/
	* oacc-mem.c (goacc_exit_data_internal): Unlock on error path.

(cherry picked from commit 2e24d457d8c97e409549848715ff046cfa9efd3d)

libgomp/oacc-mem.c

@@ -1060,7 +1060,10 @@ goacc_exit_data_internal (struct gomp_device_descr *acc_dev, size_t mapnum,
 	      = splay_tree_lookup (&acc_dev->mem_map, &cur_node);
 
 	    if (n == NULL)
-	      gomp_fatal ("struct not mapped for detach operation");
+	      {
+		gomp_mutex_unlock (&acc_dev->lock);
+		gomp_fatal ("struct not mapped for detach operation");
+	      }
 
 	    gomp_detach_pointer (acc_dev, aq, n, hostaddr, finalize, NULL);
 	  }