i965: Move blorp resolve setup into brw_blorp_blit_miptrees().

i965: Move blorp resolve setup into brw_blorp_blit_miptrees().

There was some comment about trying to avoid marking resolves in
updownsample, but if the downsample is never actually rendered to, then
the required resolve tracked in the downsample will never be executed, so
who cares?

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>