max17042: propagate of_node to power supply device

max17042_get_status uses the core power_supply_am_i_supplied. That
function relies on DT properties to figure out the power supply
topology, and will error out without DT.

Fixes max17042 battery status being reported as "unknown".

Signed-off-by: Pierre Bourdon <delroth@google.com>
Signed-off-by: Andre Heider <a.heider@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>