drm/i915: use graphics version instead of PCH split in error capture

Avoid using PCH checks in core i915 code, in preparation for moving PCH
handling to display.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://lore.kernel.org/r/8d73eb1d56603210003554bc6a875c53ed4c692a.1744630147.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>