regulator: DA9055 regulator driver

This is the Regulator patch for the DA9055 PMIC and has got dependency on
the DA9055 MFD core.

This patch support all of the DA9055 regulators. The output voltages are
fully programmable through I2C interface only. The platform data with regulation
constraints is passed down from the board to the regulator.

This patch is functionaly tested on SMDK6410 board. DA9055 Evaluation board
was connected to the SMDK6410 board.

Signed-off-by: David Dajun Chen <dchen@diasemi.com>
Signed-off-by: Ashish Jangam <ashish.jangam@kpitcummins.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>