arm64: dts: ls1028a: disable all enetc ports by default

There are few boards that enable all ENETC ports, so instead of having
board DTs disable them, do so in the DTSI and have the boards enable the
ports they use.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>