i965: Count occlusion query samples for CopyPixels using the 2D engine.

i965: Count occlusion query samples for CopyPixels using the 2D engine.

We accidentally "fixed" the piglit test for this when introducing Y
tiling, since this path stopped being executed.  In reenabling this path
for Y tiling, we ended up regressing it again, so just fix it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=59439
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>