i965/drm: Make brw_bo_alloc_tiled take tiling by value, not pointer.

i965/drm: Make brw_bo_alloc_tiled take tiling by value, not pointer.

For some reason we passed tiling by pointer, through several layers,
even though the functions only read the initial value, and never
actually change it.  We even had a do-while loop that executed until
the tiling mode matched - except it always did, so it only ran once.
We then had bogus error handling in case it changed the tiling mode
to something nonsensical...which it never did.

Drop all this nonsense.

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