drm/xe/mocs: Determine MCR separately for primary/media GT in kunit test

Although MOCS registers became multicast in graphics version 12.50 on
the primary GT, this transition did not happen until version 20 on the
media GT.  Considering each GT independently is mostly important for
MTL/ARL where the Xe_LPM+ IP has non-MCR MOCS registers, even though
Xe_LPG IP has MCR registers.

Bspec: 67789, 71186
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240314195825.3226856-3-matthew.d.roper@intel.com