ibm_newemac: Cleanup/Fix RGMII MDIO support detection

More than just "AXON" version of EMAC RGMII supports MDIO, so replace
the current test with a generic property in the device-tree that
indicates such support.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Stefan Roese <sr@denx.de>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/arch/powerpc/boot/dts/sequoia.dts b/arch/powerpc/boot/dts/sequoia.dts
index 8833dfe..3d0dfae 100644
--- a/arch/powerpc/boot/dts/sequoia.dts
+++ b/arch/powerpc/boot/dts/sequoia.dts
@@ -245,6 +245,7 @@
 				device_type = "rgmii-interface";
 				compatible = "ibm,rgmii-440epx", "ibm,rgmii";
 				reg = <ef601000 8>;
+				has-mdio;
 			};
 
 			EMAC0: ethernet@ef600e00 {