i965/gen7: Set up surface horizontal alignment field.

i965/gen7: Set up surface horizontal alignment field.

This is required for Z16 support for texturing, which is the first
thing to have a horizontal alignment of 8.  Renderbuffers don't need
it, since they're always set up as the only mip level, but do it for
completeness anyway.

NOTE: This is a candidate for the 8.0 branch.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>