[PATCH] ppc64: add ioprio syscalls

- Clean up sys32_getpriority comment.
- Add ioprio syscalls, and sign extend 32bit versions.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>