lockd: fix arg parsing for grace_period and timeout.

If you try to set grace_period or timeout via a module parameter
to lockd, and do this on a big-endian machine where

   sizeof(int) != sizeof(unsigned long)

it won't work.  This number given will be effectively shifted right
by the difference in those two sizes.

So cast kp->arg properly to get correct result.

Cc: stable@kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>