drm/xe/uapi: Add _FLAG to uAPI constants usable for flags

drm/xe/uapi: Add _FLAG to uAPI constants usable for flags

Most constants defined in xe_drm.h which can be used for flags are
named DRM_XE_*_FLAG_*, which is helpful to identify them. Make this
systematic and add _FLAG where it was missing.

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