The Hardkernel Odroid Go Ultra poweroff scheme requires requesting a poweroff
to its two PMICs in order, this represents the poweroff scheme needed to complete
a clean poweroff of the system.

This implement this scheme by implementing a self registering driver to permit
using probe defer until both pmics are finally probed.
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>