drm/i915/gvt_mmio_table: Use the gvt versions of the display macros

drm/i915/gvt_mmio_table: Use the gvt versions of the display macros

Include gvt/display_helpers.h so that the display register macros in
intel_gvt_mmio_table.c expand through the exported display functions.
This lets us keep the existing macro calls while avoiding direct
access to display internals, helping the display modularization work.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patch.msgid.link/20260114025456.1639171-1-ankit.k.nautiyal@intel.com