drm/i915/dg1: Define MOCS table for DG1

DG1 has a new MOCS table. We still use the old definition of the table,
but as for any dgfx card it doesn't contain the control_value values
(these values don't matter as we won't program them).

Bspec: 45101

v2: Reword the comment to state that the last few entries are reserved
    instead of "the last two". DG1 reserves four instead of two from
    previous platforms (from Matt Roper)

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201007002210.3678024-3-lucas.demarchi@intel.com