Convert CONFIG_OVERWRITE_ETHADDR_ONCE to Kconfig

This converts the following to Kconfig:
   CONFIG_OVERWRITE_ETHADDR_ONCE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/eb_cpu5282_defconfig b/configs/eb_cpu5282_defconfig
index a831c1c..7304b49 100644
--- a/configs/eb_cpu5282_defconfig
+++ b/configs/eb_cpu5282_defconfig
@@ -32,6 +32,7 @@
 CONFIG_CMD_MII=y
 CONFIG_MII_INIT=y
 CONFIG_CMD_DATE=y
+CONFIG_OVERWRITE_ETHADDR_ONCE=y
 CONFIG_SYS_FAULT_ECHO_LINK_DOWN=y
 CONFIG_SYS_RX_ETH_BUFFER=8
 CONFIG_SYS_I2C_LEGACY=y