drm/xe/uapi: Split xe_sync types from flags

Let's continue on the uapi clean-up with more splits
with stuff into their own exclusive fields instead of
reusing stuff.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>