ceph: drop special-casing for ITER_PIPE in ceph_sync_read

This special casing was added in 7ce469a5 (ceph: fix splice
read for no Fc capability case). The confirm callback for ITER_PIPE
expects that the page is Uptodate and returns an error otherwise.

A simpler workaround is just to use the Uptodate bit, which has no
meaning for anonymous pages. Rip out the special casing for ITER_PIPE
and just SetPageUptodate before we copy to the iter.

Cc: John Hubbard <jhubbard@nvidia.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>