OCTPHY: Ensure we write the phy-netdev parameter
OCTPHY: Ensure we write the phy-netdev parameter

When writing the config file from the command line, we must not forget
to write the phy-netdev parameter, otherwise the program will fail to
re-start later :/

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts