r8152: Use MAC address from correct device tree node

Query the USB device's device tree node when looking for a MAC address.
The struct device embedded into the struct net_device does not have a
device tree node attached at all.

The reason why this went unnoticed is because the system where this was
tested was one of the few development units that had its OTP programmed,
as opposed to production systems where the MAC address is stored in a
separate EEPROM and is passed via device tree by the firmware.

Reported-by: EJ Hsu <ejh@nvidia.com>
Fixes: acb6d377

 ("r8152: Use MAC address from device tree if available")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: EJ Hsu <ejh@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>