i965/blorp: Don't resolve HiZ unless we're reinterpreting

i965/blorp: Don't resolve HiZ unless we're reinterpreting

This eliminates 50% of pixels (2M) rendered for a blit in GS:GO.  This
accounts for 3% of pixels rendered in the game.  Total GPU clocks for
the first 900 frames of CSGO improves by 1%.

Tested-by: Mark Janes <mark.a.janes@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>