Now that we are doing a better job of managing LRZ, add support for the
EARLY_LRZ_LATE_Z mode.  Since we properly disable LRZ write in cases
where we don't know a fragment's z value during the binning pass (or
when blend is enabled in a later draw, meaning we will need the earlier
fragment's color), we can enable a mode that keeps the early-lrz test
when the frag shader has kill/discard.  This will only discard geometry
that is definitely not visible.

This is a pretty big win for games/benchmarks that have a lot of frag
shaders with kill/discard.  More than 10% gain for gfxbench trex/mh and
40% gain for mh31.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <mesa!5298>