rockchip: Enable ETH address randomization for the firefly-rk3288

This commit enables ethernet MAC address randomization on the
firefly-rk3288. It removes the error at startup 'ethernet@ff290000
address not set'.

Signed-off-by: Romain Perier <romain.perier@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/firefly-rk3288_defconfig b/configs/firefly-rk3288_defconfig
index f492f69..00bfca0 100644
--- a/configs/firefly-rk3288_defconfig
+++ b/configs/firefly-rk3288_defconfig
@@ -29,6 +29,7 @@
 CONFIG_SPL_OF_CONTROL=y
 CONFIG_OF_SPL_REMOVE_PROPS="pinctrl-0 pinctrl-names clock-names interrupt-parent assigned-clocks assigned-clock-rates assigned-clock-parents"
 CONFIG_SPL_OF_PLATDATA=y
+CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_REGMAP=y
 CONFIG_SPL_REGMAP=y
 CONFIG_SYSCON=y