net: atlantic: unify MAC generation

This patch unifies invalid MAC address handling with other drivers.

Basically we've switched to using standard APIs (is_valid_ether_addr /
eth_hw_addr_random) where possible.
It's worth noting that some of engineering Aquantia NICs might be
provisioned with a partially zeroed out MAC, which is still invalid,
but not caught by is_valid_ether_addr(), so we've added a special
handling for this case.

Also adding a warning in case of fallback to random MAC, because
this shouldn't be needed on production NICs, they should all be
provisioned with unique MAC.

NB! Default systemd/udevd configuration is 'MACAddressPolicy=persistent'.
    This causes MAC address to be persisted across driver reloads and
    reboots. We had to change it to 'none' for verification purposes.

Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>