ceph: pass filp to ceph_get_caps()

Also change several other functions' arguments, no logical changes.
This is preparetion for later patch that checks filp error.

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