max8925_power: Enable power change notifications

The power core infrastructure allow external power change
events to be passed to drivers what are listed in the
supplied_to call back field.  Enable this feature by
allowing the supplied_to field to be passed to the driver.

This feature will enable drivers named in the supplied_to
field that have a external_power_changed callback to be
notified when power was been turned on or off.

Signed-off-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>