ethmngr: remove handling of ports.@ethport[i].enabled
The handling of this option for Linux and Broadcom is moved to a netifd patch as handling it from scripts interferes with netifd operation. Only netifd can be allowed to bring Linux interfaces up/down using SIOCSIFFLAGS. Otherwise things end up out of sync.
The same applies to phy-power for Broadcom as it gets set indirectly when IFF_UP is set via SIOCSIFFLAGS. The phy-reset must be removed as well as it powers the port up.
Note this is dependent on: openwrt-core!351 (closed)