regulator: Add Freescale MC13783 driver

This driver provides basic support for the voltage regulators
integrated into the Freescale MC13783 PMIC. It is currently
only possible to enable/disable outputs, not to actually
set the voltage.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>