power: pmic: add driver for Dialog DA9063 PMIC

This adds the basic register access operations and child regulator
binding (if a regulator driver exists).

Robert Beckett: simplify accesses by using bottom bit of address as
offset overflow. This avoids the need to track which page we are on.
Add an option CONFIG_SPL_DM_PMIC_DA9063.

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