mesa/subroutines: drop the old subroutine index uploads.

mesa/subroutines: drop the old subroutine index uploads.

We used to upload the indices when they changed, now we rely
on the drivers calling the correct hook to have the values
updated from the context storage.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Andres Gomez <agomez@igalia.com>