regulator: Updates for v4.20 This has been a very busy release for the core, some fixes, one large new feature and a big bit of refactoring to update the GPIO API: - Support for coupled regulators from Dmitry Osipenko based on a prior attempt by Maciej Purski, allowing us to handle situations where the voltages on two regulators can't be too far apart from each other. - Conversion of the GPIO support in both drivers and the core to use GPIO descriptors rather than numbers, part of the overall project to remove GPIO numbers. - Support for standby mode suspend states from Andrei Stefanescu. - New drivers for Allwinner AXP209, Cirrus Logic Lochnagar and Microchip MPC16502.