i965: Push intel_get_texture_alignment_unit call into brw_miptree_layout

i965: Push intel_get_texture_alignment_unit call into brw_miptree_layout

intel_miptree_create_layout() calls intel_get_texture_alignment_unit()
and then immediately calls brw_miptree_layout().  There are no other
callers.

intel_get_texture_alignment_unit() populates the miptree's alignment
unit fields, which are used by brw_miptree_layout() to determine where
to place each miplevel.  Since brw_miptree_layout() needs those to be
present, it makes sense to have it initialize them as the first step.

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