vulkan/x11: use xcb_connection_has_error to check for failue

xcb_connectxx() always returns a non-NULL pointer to a
xcb_connection_t, even on failure.

cc: mesa-stable

Signed-off-by: YaoBing Xiao <xiaoyaobing@uniontech.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31812>

src/vulkan/device-select-layer/device_select_x11.c

@@ -70,8 +70,10 @@ int device_select_find_xcb_pci_default(struct device_pci_info *devices, uint32_t
   drmDevicePtr xdev = NULL;
 
   conn = xcb_connect(NULL, &scrn);
-  if (!conn)
+  if (xcb_connection_has_error(conn)) {
+    xcb_disconnect(conn);
     return -1;
+  }
 
   xcb_query_extension_cookie_t dri3_cookie;
   xcb_query_extension_reply_t *dri3_reply = NULL;