drm/i915/dg2: Add new LRI reg offsets

New LRI register offsets were introduced for DG2, this patch adds
those extra registers, and create new register table for setting offsets
to compare with HW generated context image - especially for gt_lrc test.
Also updates general purpose register with scratch offset for DG2, in
order to use it for live_lrc_fixed selftest.

Cc: Chris P Wilson <chris.p.wilson@intel.com>
Cc: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Caz Yokoyama <caz.yokoyama@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210805163647.801064-8-matthew.d.roper@intel.com