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Now that the GGTT PTE updates go straight to GSMBASE (bypassing
GTTMMADR) there should be no more risk of system hangs? So the
"binder" (ie. update the PTEs via MI_UPDATE_GTT) is no longer
necessary, disable it.

My main worry with the MI_UPDATE_GTT are:
- only used on this one platform so very limited testing coverage
- async so more opprtunities to screw things up
- what happens if the engine hangs while we're waiting for MI_UPDATE_GTT
  to finish?
- requires working command submission, so even getting a working
  display now depends on a lot more extra components working correctly

TODO: MI_UPDATE_GTT might be interesting as an optimization
though, so perhaps someone should look into always using it
(assuming the GPU is alive and well)?

v2: Keep using MI_UPDATE_GTT on VM guests
v3: use i915_direct_stolen_access()
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Tested-by: Paz Zcharya <pazz@chromium.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240202224340.30647-6-ville.syrjala@linux.intel.com