drm/i915: disable platform support for vGPU huge gtt pages

drm/i915: disable platform support for vGPU huge gtt pages

Currently gvt gtt handling doesn't support huge page entries, so disable
for now.

v2: remove useless 48b PPGTT check

Suggested-by: Zhenyu Wang <[email protected]>
Signed-off-by: Matthew Auld <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Zhenyu Wang <[email protected]>
Reviewed-by: Zhenyu Wang <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]