ceph: fix non static symbol warning

Fixes the following sparse warning:

fs/ceph/xattr.c:19:28: warning:
 symbol 'ceph_other_xattr_handler' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>