drm/xe/mocs: Clarify which GT is being operated on

Switch the MOCS-related debug messages to use a GT-specific logging
function and add ID/type output to the beginning of the MOCS kunit test
to assist with debug when problems arise.

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/20240314195825.3226856-4-matthew.d.roper@intel.com