arm: mvebu: clearfog_defconfig: enable setexpr command

This command is useful in U-boot scripts and it is being used by
OpenWrt bootscript for this board [1]. Otherwise shell scripting
commands are enabled by default in cmd/Kconfig.

[1] https://github.com/openwrt/openwrt/blob/852126680e21edc71c0c66561ae5a6d7479dcc67/target/linux/mvebu/image/clearfog.bootscript#L7

[2] https://source.denx.de/u-boot/u-boot/-/blob/e95afa56753cebcd20a5114b6d121f281b789006/cmd/Kconfig#L1504

Fixes: 0299c90f396c5b2971a4bac596339f4b03661c27 ("arm: mvebu: Add
SolidRun ClearFog Armada 38x initial support")

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/configs/clearfog_defconfig b/configs/clearfog_defconfig
index 880f16a..1e9c389 100644
--- a/configs/clearfog_defconfig
+++ b/configs/clearfog_defconfig
@@ -34,7 +34,6 @@
 CONFIG_CMD_PCI=y
 CONFIG_CMD_SPI=y
 CONFIG_CMD_USB=y
-# CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_TFTPPUT=y
 CONFIG_CMD_CACHE=y
 CONFIG_CMD_TIME=y