dt-bindings: net: mvneta: Add marvell,armada-ac5-neta

The out of band port on the 98DX2530 SoC is similar to the armada-3700
except it requires a slightly different MBUS window configuration. Add a
new compatible string so this difference can be accounted for.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>