drm/nouveau/pmu/fuc: use the call macro instead of using the call instruction directly

the macro deals with target specific differences and so we should always use
this

Signed-off-by: Karol Herbst <nouveau@karolherbst.de>
Reviewed-by: Martin Peres <martin.peres@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>