drm/xe/tests: Skip xe_mocs live tests on VF device

There is no point to run those tests on VFs devices as they can't
access any of the MOCS registers. Skip testing on the VF device.

  [ ] =================== xe_mocs (1 subtest) ====================
  [ ] ================ xe_live_mocs_kernel_kunit  ================
  [ ] [PASSED] 0000:4d:00.0
  [ ] [SKIPPED] 0000:4d:00.1
  [ ] ============ [PASSED] xe_live_mocs_kernel_kunit ============
  [ ] ===================== [PASSED] xe_mocs =====================

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240720142528.530-8-michal.wajdeczko@intel.com