net: dm: Remove warning about EEPROM provided MAC address

net: dm: Remove warning about EEPROM provided MAC address

Similar to patch 821fec0ceb3e ("net: remove scary warning about EEPROM
provided MAC address") this removes the somewhat awkward "warning" on
boards using DM_ETH:
In many parts of the computing world having a unique MAC address
sitting in some on-NIC storage is considered the normal case.

If there is a properly provided MAC address (either from ROM or from DT),
remove the warning to not scare the user unnecessarily.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-By: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>