btrfs: avoid error code override in btrfs_get_acl

It's not good to override the error code when failing from
btrfs_getxattr() in btrfs_get_acl() because it hides the real reason of
the failure.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/acl.c

@@ -45,7 +45,7 @@ struct posix_acl *btrfs_get_acl(struct inode *inode, int type)
 	} else if (size == -ENODATA || size == 0) {
 		acl = NULL;
 	} else {
-		acl = ERR_PTR(-EIO);
+		acl = ERR_PTR(size);
 	}
 	kfree(value);