intel/hsw: Enable hiz (v2)

intel/hsw: Enable hiz (v2)

Enable hiz by setting intel_context::has_hiz.  However, to work around
a hardware bug, we selectively enable hiz for only nicely aligned miptree
slices.

No Piglit regressions on Haswell 0x0d26 rev07 when based atop
mesa-master-4ad3601.

Improves the performance of GLB27_TRex_C24Z16_FixedTimeStep by 18.52%
(hsw-0x0d26-rev07; kernel-3.9.0-rc1; GLBenchmark 2.7.0 Release a68901;
samples=3).

v2: Replace the check for IS_HASWELL(devid) in intel_miptree_slice_has_hiz()
    with a conditional set of has_hiz. [for anholt]

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>