bcachefs: Remove a redundant and harmless bch2_free_super() call

Remove a redundant call to bch2_free_super().

This is harmless because bch2_free_super() has a memset() at its end. So
a second call would only lead to from kfree(NULL).

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

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/super.c

@@ -1605,7 +1605,6 @@ int bch2_dev_add(struct bch_fs *c, const char *path)
 
 	ca = __bch2_dev_alloc(c, &dev_mi);
 	if (!ca) {
-		bch2_free_super(&sb);
 		ret = -ENOMEM;
 		goto err;
 	}