Complete the documentation of some structs by adding functional
examples of user space code. Those examples are intentionally kept
very simple. Put together, they provide a foundation for a minimal
application that executes a job using the Xe driver.

v2: Remove use of DRM_XE_VM_BIND_FLAG_ASYNC (Francois Dugast)
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: José Roberto de Souza <jose.souza@intel.com>
Acked-by: Mateusz Naklicki <mateusz.naklicki@intel.com>
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>