regulator: Updates for v3.12 Not much exciting going on with the regulator API this time around, lots of driver fixes and enhancements - the main thing is the addition of a new API to help make the stubbing code do the right thing for missing regulator mappings. Highlights: - A new regulator_get_optional() API call for regulators that can be absent in normal operation. This currently does nothing but will be used to improve the stubbing code for unspecified regulators, helping avoid some of the issues we've seen with adding new regulator support. - Helpers for devices with multiple linear ranges of voltages in the same regulator. - Moved the helpers into a separate file since core.c is getting rather large. - New drivers for Dialog DA9210 and DA9063, Freescale pfuze100 and Marvell 88pm800.