drm/xe: Invalidate media_gt TLBs in PT code

drm/xe: Invalidate media_gt TLBs in PT code

Testing on LNL has shown media GT's TLBs need to be invalidated via the
GuC, update PT code appropriately.

v2:
 - Do dma_fence_get before first call of invalidation_fence_init (Himal)
 - No need to check for valid chain fence (Himal)

Fixes: 3330361543fc ("drm/xe/lnl: Add LNL platform definition")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240820161632.987369-1-matthew.brost@intel.com