ARM: kirkwood: SBx81LIFKW: enable CONFIG_NET_RANDOM_ETHADDR

When booting a fresh board having a random Ethernet address enables
using the network device to program the board.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/configs/SBx81LIFKW_defconfig b/configs/SBx81LIFKW_defconfig
index ec940bd..a9f9842 100644
--- a/configs/SBx81LIFKW_defconfig
+++ b/configs/SBx81LIFKW_defconfig
@@ -39,6 +39,7 @@
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_ENV_SPI_MAX_HZ=20000000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
+CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_NETCONSOLE=y
 CONFIG_DM=y
 CONFIG_DM_PCA953X=y