drm/i915: Move GMD_ID and mask to intel_gt header
GMD_ID* is relevant only for GT, hence moving the same
together in gt/intel_gt_regs.h
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patch.msgid.link/20260205094341.1882816-8-uma.shankar@intel.com