drm/nouveau/pm: make clocks_set return an error code clocks_set can fail.

Reporting an error is better than silently refusing to reclock.

V2: Use the same logic on nv40

Signed-off-by: Martin Peres <martin.peres@labri.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
4 files changed