Comment 33 for bug 1275794

Dropping just the config.mutex is dangerous, especially when we also call this function from the disable/enable hooks where we always also hold the relevant crtc->mutex.

I wonder a bit though who's hogging the kms lock - we chase an awful lot of pointers to get at it, so if someone's corrupting this I expect we'd blow up. And lockdep shouldn't be too happy about it either. Confusing.