bcachefs: Fix use-after-free in bch2_dev_add()

If __bch2_dev_attach_bdev() fails, bch2_dev_free() is called twice.
Once here and another time in the error handling path.

This leads to several use-after-free.

Remove the redundant call and only rely on the error handling path.

Fixes: 6a44735653d4 ("bcachefs: Improved superblock-related error messages")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/super.c

@@ -1613,10 +1613,8 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 	bch2_dev_usage_init(ca);
 
 	ret = __bch2_dev_attach_bdev(ca, &sb);
-	if (ret) {
-		bch2_dev_free(ca);
+	if (ret)
 		goto err;
-	}
 
 	ret = bch2_dev_journal_alloc(ca);
 	if (ret) {