i965/miptree: Refactor intel_miptree_resolve_color

i965/miptree: Refactor intel_miptree_resolve_color

The new version now takes a range of levels as well as a range of
layers.  It should also be a tiny bit faster because it only walks the
resolve_map list once instead of once per layer.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Chad Versace <chadversary@chromium.org>