intel: Add map_stencil_as_y_tiled to intel_region_get_aligned_offset.

intel: Add map_stencil_as_y_tiled to intel_region_get_aligned_offset.

This patch modifies intel_region_get_aligned_offset() to make the
appropriate calculation when the blorp engine sets up a W-tiled
stencil buffer using a Y-tiled SURFACE_STATE.

NOTE: This is a candidate for stable release branches.

Acked-by: Eric Anholt <eric@anholt.net>