reiserfs: fixup perms when xattrs are disabled

This adds CONFIG_REISERFS_FS_XATTR protection from reiserfs_permission.

This is needed to avoid warnings during file deletions and chowns with
xattrs disabled.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>