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/mx6sabresd_spl_defconfig b/configs/mx6sabresd_spl_defconfig
index 0589c48..ab40558 100644
--- a/configs/mx6sabresd_spl_defconfig
+++ b/configs/mx6sabresd_spl_defconfig
@@ -2,3 +2,4 @@
 CONFIG_TARGET_MX6SABRESD=y
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg,SPL,MX6Q"
+CONFIG_CMD_SETEXPR=y