bcachefs: acl: Uninitialized variable in bch2_acl_chmod()

The clean up code at the end of the function uses "acl" so it needs
to be initialized to NULL.

Fixes: 53306e096d91 ("bcachefs: Always check for transaction restarts")
Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Kent Overstreet <[e-mail]>

fs/bcachefs/acl.c

···
 	struct btree_iter iter;
 	struct bkey_s_c_xattr xattr;
 	struct bkey_i_xattr *new;
-	struct posix_acl *acl;
+	struct posix_acl *acl = NULL;
 	struct bkey_s_c k;
 	int ret;