vfio/common: return early if space isn't empty

This is a trivial optimization. If there is active container in space,
vfio_reset_handler will never be unregistered. So revert the check of
space->containers and return early.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/common.c

@@ -1462,10 +1462,13 @@ VFIOAddressSpace *vfio_get_address_space(AddressSpace *as)
 
 void vfio_put_address_space(VFIOAddressSpace *space)
 {
-    if (QLIST_EMPTY(&space->containers)) {
-        QLIST_REMOVE(space, list);
-        g_free(space);
+    if (!QLIST_EMPTY(&space->containers)) {
+        return;
     }
+
+    QLIST_REMOVE(space, list);
+    g_free(space);
+
     if (QLIST_EMPTY(&vfio_address_spaces)) {
         qemu_unregister_reset(vfio_reset_handler, NULL);
     }