Move setexpr to Kconfig

Another shell scripting command that has not been moved.

Moved using tools/moveconfig.py using these settings:

CMD_SETEXPR bool n y

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/configs/riotboard_defconfig b/configs/riotboard_defconfig
index ae0036a..a53ee94 100644
--- a/configs/riotboard_defconfig
+++ b/configs/riotboard_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_TARGET_EMBESTMX6BOARDS=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6s1g.cfg,MX6S,DDR_MB=1024,ENV_IS_IN_MMC"
+CONFIG_CMD_SETEXPR=y
 CONFIG_DM=y
 CONFIG_DM_THERMAL=y