net: dsa: sja1105: be compatible with "ethernet-ports" OF node name

Since commit f2f3e09396be ("net: dsa: sja1105: be compatible with
"ethernet-ports" OF node name"), DSA supports the "ethernet-ports" name
for the container node of the ports, but the sja1105 driver doesn't,
because it handles some device tree parsing of its own.

Add the second node name as a fallback.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>