drm/i915/mtl: Add Wa_14019821291

This workaround is primarily implemented by the BIOS.  However if the
BIOS applies the workaround it will reserve a small piece of our DSM
(which should be at the top, right below the WOPCM); we just need to
keep that region reserved so that nothing else attempts to re-use it.

v2: Declare regs in intel_gt_regs.h (Matt Roper)

v3: Shift WA implementation before calculation of *base (Matt Roper)

v4:
-  Change condition gscpmi base to be fall in DSM range.(Matt Roper)

Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231027195052.3676632-1-dnyaneshwar.bhadane@intel.com