intel: Use drm_intel_bo_alloc_tiled for region allocs.

intel: Use drm_intel_bo_alloc_tiled for region allocs.

This moves the logic for how to align pitches, heights, and sizes of
objects to one central location.  Fixes rendering with texture tiling
on i915.  Note that current libdrm is required for the change for
I915_TILING_NONE pitch alignment.