i965/drm: Make brw_bo_alloc_tiled flags parameter 32-bit.

i965/drm: Make brw_bo_alloc_tiled flags parameter 32-bit.

unsigned long is a terrible type for a bitfield - if you need fewer
than 32 bits, it wastes 4 bytes.  If you need more, things break on
32-bit builds.  Just use unsigned.

Even that's a bit ridiculous as we only have one flag today.
Still, it's at least somewhat better.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>