drm/xe/bo: consider dma-resv fences for clear job

There could be active fences already in the dma-resv for the object
prior to clearing. Make sure to input them as dependencies for the clear
job.

v2 (Matt B):
  - We can use USAGE_KERNEL here, since it's only the move fences we
    care about here. Also add a comment.

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