ceph: add object version support for sync read

Turn the guts of ceph_sync_read into a new helper that takes an inode
and an offset instead of a kiocb struct, and make ceph_sync_read call
the helper as a wrapper.

Make the new helper always return the last object's version.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-and-tested-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>