[PARISC] Add new ioprio_{set,get} syscalls

add syscall entries for ioprio_set/get as per Jens Axboe.

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Grant Grundler <grundler@parisc-linux.org>

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>