ARM: mvebu: correct reference for "ethernet1" on DB-88F6820-AMC

The DB-88F6820-AMC connects ethernet@34000 and ethernet@70000 which are
labeled as eth2 and eth0 in armada-38x.dts. The ethernet@30000 (eth1) is
not used on the AMC board.

This eliminates the following bootup message

  Device 'ethernet@70000': seq 0 is in use by 'ethernet@34000'

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Signed-off-by: Stefan Roese <sr@denx.de>

arch/arm/dts/armada-385-amc.dts

@@ -53,7 +53,7 @@
 
 	aliases {
 		ethernet0 = &eth0;
-		ethernet1 = &eth1;
+		ethernet1 = &eth2;
 		i2c0 = &i2c0;
 		spi1 = &spi1;
 	};