drm/i915/gen8: Create separate reg definitions for new MCR registers

Gen8 was the first time our hardware had multicast registers (or at
least the first time the multicast nature was exposed and MMIO accesses
could be steered).  There are some registers that transitioned from
singleton behavior to multicast during the gen7 -> gen8 transition;
let's duplicate the register definitions for those registers in
preparation for upcoming patches that will handle MCR registers in a
special manner.

The registers adjusted are:
 * MISCCPCTL
 * SAMPLER_INSTDONE
 * ROW_INSTDONE
 * ROW_CHICKEN2
 * HALF_SLICE_CHICKEN1
 * HALF_SLICE_CHICKEN3

v2:
 - Use the gen8 version of HALF_SLICE_CHICKEN3 in GVT's gen9 engine MMIO
   list.  (Bala)
 - Update to the gen8 version of MISCCPCTL in a couple new workarounds
   that were recently added for DG2/PVC.  (Bala)

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014230239.1023689-2-matthew.d.roper@intel.com