[rfc] fix output poll execute lockdep

[Dave Airlie]

On runtime resume, nouveau can try and take the mode_config
mutex in the poll reenable, however a poll can race with this,
and take the mutex and get stuck waiting for the runtime to
finish completion. These two patches allow the driver to
get hooked in before the mutex is taken.

I think radeon/amdgpu will also need similar patches to nouveau.

I found this while trying to track down a runtime regression
on W541 laptop, I'm not sure I found what the reporter was seeing yet.

Dave.