drm/sysfs lifetime interaction fixes

[Dave Airlie]

>>
>> This is my preferred method of fixing it as I don't think the lifetimes need
>> to be tied so closely, though this requires review my someone to make sure
>> my unregistering etc is correct and in the right place.
>
> Apparently this fixes the problem for Fengguang, and the code looks
> cleaner too. Thanks,

Leaves the fixes or next question, since I suppose its not technically
a regression, -next is probably fine, let me know if you'd l like them
earlier.

Dave.