net: cosmetic: Name ethaddr variables consistently

Use "_ethaddr" at the end of variables and drop CamelCase.
Make constant values actually 'const'.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/board/renesas/r0p7734/r0p7734.c b/board/renesas/r0p7734/r0p7734.c
index 5687ad4..2e31ba6 100644
--- a/board/renesas/r0p7734/r0p7734.c
+++ b/board/renesas/r0p7734/r0p7734.c
@@ -55,7 +55,7 @@
 	/* Read MAC address */
 	i2c_read(0x50, 0x10, 0, mac, 6);
 
-	if (is_valid_ether_addr(mac))
+	if (is_valid_ethaddr(mac))
 		eth_setenv_enetaddr("ethaddr", mac);
 
 	return 0;