dt-bindings: net: korina: Add DT bindings for IDT 79RC3243x SoCs

Add device tree bindings for ethernet controller integrated into
IDT 79RC3243x SoCs.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: David S. Miller <davem@davemloft.net>