drm/xe/tlb: Obtain forcewake when doing GGTT TLB invalidations

Updates to the GGTT can happen when there are no in-flight jobs keeping
the hardware awake.  If the GT is powered down when invalidation is
requested, we will not be able to communicate with the GuC (or MMIO) and
the invalidation request will go missing.  Explicitly grab GT forcewake
to ensure the GT and GuC are powered up during the TLB invalidation.

Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Link: https://lore.kernel.org/r/20230601215244.678611-28-matthew.d.roper@intel.com


Signed-off-by: Matt Roper <matthew.d.roper@intel.com>