mfd: da9063: Add Dialog DA9063 core driver

This is MFD module providing access to registers and interrupts of DA906x
series PMIC. It is used by other functional modules, registered as MFD cells.
Driver uses regmap with paging to access extended register list. Register map
is divided into two pages, where the second page is used during initialisation.

This module provides support to following functional cells:
 - Regulators
 - RTC
 - HWMON
 - OnKey (power key misc input device)
 - Vibration (force-feedback input device)
 - Watchdog
 - LEDs

Signed-off-by: Krystian Garbaciak <krystian.garbaciak@diasemi.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>