drm/sched: Fix make htmldocs warnings.

Document the missing parameters.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1559140180-6762-1-git-send-email-andrey.grodzovsky@amd.com