pohmelfs: Remove dead quota code

Quota on pohmelfs is non-functional. IFAIU quota logic was copy-pasted
from generic setattr().

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>