quota: Remove bogus 'optimization' in check_idq() and check_bdq()

Checks like <= 0 for an unsigned type do not make much sence. The value
could be only 0 and that does not happen often enough for the check
to be worth it.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>