drm/xe/vf: Don't use register based TLB invalidation if VF

VF drivers can only use GuC-based TLB invalidation, as they don't
have access to the related registers. However, VFs shouldn't need
any explicit TLB invalidation before enabling CTB communication,
as there will be an implicit GGTT TLB invalidation issued by the
GuC itself as part of MMIO-based action handling.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240619214557.905-8-michal.wajdeczko@intel.com