drm/xe/uapi: Kill DRM_XE_UFENCE_WAIT_VM_ERROR

This is not used nor does it align VM async document, kill this.

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