drm/i915: Use per-plane VT-d guard numbers

drm/i915: Use per-plane VT-d guard numbers

Bspec lists different VT-d guard numbers (the number of dummy
padding PTEs) for different platforms and plane types. Use those
instead of just assuming the max glk+ number for everything.
This could avoid a bit of overhead on older platforms due to
reduced padding, and it makes it easier to cross check with the
spec.

Note that VLV/CHV do not document this w/a at all, so not sure
if it's actually needed or not. Nor do we actually know how much
padding is required if it is needed. For now use the same 128
PTEs that we use for snb-bdw primary planes.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250122151755.6928-5-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>