drm/nouveau/fan: restore pwm value on resume when in manual/auto mode

If the fan was in manual or auto mode, we should restore the fan speed
that was previously set when resuming.

The initial pwm value is saved when loading the module.

Signed-off-by: Martin Peres <martin.peres@labri.fr>
Tested-by: Martin Peres <martin.peres@labri.fr>
Tested-by: Dash Four <mr.dash.four@googlemail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>