drm/xe/vf: Don't program MOCS if VF

MOCS programming may only be done by the PF driver.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240213154355.1221-4-michal.wajdeczko@intel.com