video:uvesafb: Fix dereference NULL pointer code path

platform_device_alloc could failed and return NULL,
we should check this before call platform_device_put.
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/video/uvesafb.c

@@ -1973,6 +1973,7 @@ static int uvesafb_init(void)
 			err = -ENOMEM;
 
 		if (err) {
+			if (uvesafb_device)
 				platform_device_put(uvesafb_device);
 			platform_driver_unregister(&uvesafb_driver);
 			cn_del_callback(&uvesafb_cn_id);