dm: eth: Add support for aliases

Allow network devices to be referred to as "eth0" instead of
"eth@12345678" when specified in ethact.

Add tests to verify this behavior.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/sandbox.h b/include/configs/sandbox.h
index e225ce6..9769a8d 100644
--- a/include/configs/sandbox.h
+++ b/include/configs/sandbox.h
@@ -178,7 +178,7 @@
 
 #define SANDBOX_ETH_SETTINGS		"ethaddr=00:00:11:22:33:44\0" \
 					"eth1addr=00:00:11:22:33:45\0" \
-					"eth2addr=00:00:11:22:33:46\0" \
+					"eth5addr=00:00:11:22:33:46\0" \
 					"ipaddr=1.2.3.4\0"
 
 #define CONFIG_EXTRA_ENV_SETTINGS	SANDBOX_SERIAL_SETTINGS \