Revert the changes I applied to aa5014dd1a58 ("ramips: mt7620n: enable
port 4 as EPHY by default").
The driver expects a node mdio-bus to be present, regardless of the
actual node status. If the node is missing the driver fails to load with
mtk_soc_eth 10100000.ethernet: no mdio-bus child node found
Disable port4 by default again. If the port is enabled but not present, a
"invalid port id 4" warning is shown during boot.
Fixes: FS#1428
Signed-off-by: Mathias Kresin <dev@kresin.me>
d482356322