Btrfs: Fix setting umask when POSIX ACLs are not enabled

We currently set sb->s_flags |= MS_POSIXACL unconditionally, which is
incorrect -- it tells the VFS that it shouldn't set umask because we
will, yet we don't set it ourselves if we aren't using POSIX ACLs, so
the umask ends up ignored.
Signed-off-by: NChris Ball <cjb@laptop.org>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

fs/btrfs/super.c

@@ -344,7 +344,9 @@ static int btrfs_fill_super(struct super_block *sb,
 	sb->s_export_op = &btrfs_export_ops;
 	sb->s_xattr = btrfs_xattr_handlers;
 	sb->s_time_gran = 1;
+#ifdef CONFIG_BTRFS_POSIX_ACL
 	sb->s_flags |= MS_POSIXACL;
+#endif
 
 	tree_root = open_ctree(sb, fs_devices, (char *)data);