ceph: silence sparse endianness warning in encode_caps_cb

sparse warns:

  fs/ceph/mds_client.c:2887:34: warning: incorrect type in assignment (different base types)
  fs/ceph/mds_client.c:2887:34:    expected restricted __le32 [assigned] [usertype] flock_len
  fs/ceph/mds_client.c:2887:34:    got int

At this point, it's just being used as a flag. It gets
overwritten later if the rest of the encoding succeeds.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>