power: supply: Propagate of_node to child device

Ensure that the dynamically created power supply device sets its
->of_node if the driver supplies one.  This brings it in line with
several other subsystems (see git grep 'of_node =.*parent.*of_node') and
allows easier identification of the device from udev rules and similar.

Before this patch:

 /sys/class/power_supply# ls -l bq256xx-battery/of_node
 ls: cannot access 'bq256xx-battery/of_node': No such file or directory
 # ls -l bq256xx-battery/hwmon1/of_node
 ls: cannot access 'bq256xx-battery/hwmon1/of_node': No such file or directory

After:

 /sys/class/power_supply# ls -l bq256xx-battery/of_node
 lrwxrwxrwx 1 root root 0 May 17 09:14 bq256xx-battery/of_node ->
 ../../../../../../../../firmware/devicetree/base/virtio@1/i2c/bq25619@09
 # ls -l bq256xx-battery/hwmon1/of_node
 lrwxrwxrwx 1 root root 0 May 17 09:14 bq256xx-battery/hwmon1/of_node ->
 ../../../../../../../../../firmware/devicetree/base/virtio@1/i2c/bq25619@09

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Link: https://lore.kernel.org/r/20230915-power-of-v2-1-ca54c441867e@axis.com


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>