drm/xe: Allow dma-fences as in-syncs for compute / faulting VM

This is allowed and encouraged by the dma-fencing rules. This along with
allowing compute VMs to export dma-fences on binds will result in a
simpler compute UMD.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>