iris: Avoid unnecessary resolves on transfer maps

We were always resolving the buffer as if we were accessing it via
CPU maps, which don't understand any auxiliary surfaces.  But we often
copy to a temporary using BLORP, which understands compression just
fine.  So we can avoid the resolve, and accelerate the copy as well.

Fixes: 9d1334d2 ("iris: Use copy_region and staging resources to avoid transfer stalls")
Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>
(cherry picked from commit 2d799250)