freedreno/a6xx: fix LRZ logic

freedreno/a6xx: fix LRZ logic

In particular, we need to invalidate the LRZ state when we cannot be
confident in what the Z state would be during rendering:

1) depth test modes not supported by LRZ
2) stencil test, which would require full rasterization and stencil
   test in the binning pass (whereas LRZ normally just needs to
   determine the min and max z value in an 8x8 quad)

Signed-off-by: Rob Clark <robdclark@chromium.org>