drm/i915: Use expcitly fixed type in compat32 structs

I was confused shortly whether the compat was needed for the int,
until I noticed the pointer in the original.

Also remove typedef.

v2: Review from Chris.
- Add comments.
- Also change the int param in the original structure.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>