power: regulator: add driver for Dialog DA9063 PMIC

Add a driver for the regulators in the the DA9063 PMIC.

Robert Beckett: move regulator modes to header so board code can set
modes. Correct mode mask used in ldo_set_mode.
Add an option CONFIG_SPL_DM_REGULATOR_DA9063.

Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Signed-off-by: Robert Beckett <bob.beckett@collabora.com>