qxl/update_area_io: cleanup invalid parameters handling

This cleans up two additions of almost the same code in commits
511b13e2 and ccc2960d.  While at it, make error paths
consistent (always use 'break' instead of 'return').
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>
Cc: Dunrong Huang <riegamaths@gmail.com>
Cc: Alon Levy <alevy@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/qxl.c

@@ -1547,20 +1547,13 @@ async_common:
         if (d->ram->update_surface > d->ssd.num_surfaces) {
             qxl_set_guest_bug(d, "QXL_IO_UPDATE_AREA: invalid surface id %d\n",
                               d->ram->update_surface);
-            return;
+            break;
         }
-        if (update.left >= update.right || update.top >= update.bottom) {
+        if (update.left >= update.right || update.top >= update.bottom ||
+            update.left < 0 || update.top < 0) {
             qxl_set_guest_bug(d,
                     "QXL_IO_UPDATE_AREA: invalid area (%ux%u)x(%ux%u)\n",
                     update.left, update.top, update.right, update.bottom);
-            return;
-        }
-
-        if (update.left < 0 || update.top < 0 || update.left >= update.right ||
-            update.top >= update.bottom) {
-            qxl_set_guest_bug(d, "QXL_IO_UPDATE_AREA: "
-                              "invalid area(%d,%d,%d,%d)\n", update.left,
-                              update.right, update.top, update.bottom);
             break;
         }
         if (async == QXL_ASYNC) {