regulator: Updates for v3.13 Lots of driver updates here plus some nice new core features, the main one being the first: - Enable support for providing a dummy regulator when we know that one must exist for the device to be functional. This makes it much easier to add regulator support to drivers since we don't require that the machine integration for all systems using the device be updated to provide regulators. - Substantial reduction in the amount of busy waiting done while waiting for enables to complete. - Allow MFDs to distribute regulator supplies to child devices so we don't have to expose the internal structure of MFDs outside of the driver. - Managed registeration for regulators.