bcache: fix possible memory leak in bch_cached_dev_run()

memory malloced in bch_cached_dev_run() and should be freed before
leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: 0b13efecf5f2 ("bcache: add return value check to bch_cached_dev_run()")
Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Coly Li <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/md/bcache/super.c

···
 	if (dc->io_disable) {
 		pr_err("I/O disabled on cached dev %s",
 		       dc->backing_dev_name);
+		kfree(env[1]);
+		kfree(env[2]);
+		kfree(buf);
 		return -EIO;
 	}