i965: Consistently do depth resolves before blitting.

i965: Consistently do depth resolves before blitting.

We were protected for a long time by the fact that depth was Y tiled and
you couldn't blit Y.  Now that we can blit Y, we were failing to resolve
depth in glCopyPixels().

Note in the comment about swrast, that the swrast map path does resolves
appropriately already.

Reviewed-and-tested-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Paul Berry <stereotype441@gmail.com>