mfd: DA9055 core driver

This is the DA9055 MFD core driver that instantiate all the dependent
component drivers and provides them the device access via I2C.

This patch is functionally tested on Samsung SMDK6410.

Signed-off-by: David Dajun Chen <dchen@diasemi.com>
Signed-off-by: Ashish Jangam <ashish.jangam@kpitcummins.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>