drm/nouveau/pmu/fuc: replace mov+sethi with imm32

on gk208+ we can simply mov 32bits, so we should have a single mov there

v2: use or operator instead of add

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