fbdev: uvesafb: unregister connector callback on init failure

uvesafb_init() registers the v86d connector callback before registering
the platform driver. If platform_driver_register() fails, the function
returns the error directly and leaves the connector callback registered.

The later platform-device failure path already unregisters the callback.
Add the same cleanup before the final return when platform-driver
registration fails.

This issue was identified during our ongoing static-analysis research while
reviewing kernel code.

Fixes: 8bdb3a2d7d ("uvesafb: the driver core")
Cc: stable@vger.kernel.org
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>

drivers/video/fbdev/uvesafb.c

@@ -1907,6 +1907,8 @@ static int uvesafb_init(void)
 			err = 0;
 		}
 	}
+	if (err)
+		cn_del_callback(&uvesafb_cn_id);
 	return err;
 }