drm/nouveau/pmu: move init() falcon reset to non-nvfw code

Cleanup before falcon changes.

- fixes (attempt at?) reset of pmu while rtos is running, on gm20b

v2:
- remove extra whitespace

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>