nios2: enable setexpr command in defconfig

Enable setexpr command in defconfig because it is really
useful as suggested by Marek.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Acked-by: Marek Vasut <marex@denx.de>
diff --git a/configs/nios2-generic_defconfig b/configs/nios2-generic_defconfig
index fbc27ea..e42a15e 100644
--- a/configs/nios2-generic_defconfig
+++ b/configs/nios2-generic_defconfig
@@ -10,7 +10,6 @@
 # CONFIG_CMD_XIMG is not set
 # CONFIG_CMD_FPGA is not set
 # CONFIG_CMD_ITEST is not set
-# CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_DHCP=y
 # CONFIG_CMD_NFS is not set
 CONFIG_CMD_PING=y