nios2: move command line configuration to Kconfig

This patch moves command line configuration from board header
file to board defconfig in the way of Kconfig. The change passed
savedefconfig.

This fixes warnings such as : "CONFIG_SYS_HUSH_PARSER" redefined,
when "Use hush shell" is selected with menuconfig, etc.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
diff --git a/configs/nios2-generic_defconfig b/configs/nios2-generic_defconfig
index 573a084..5f93394 100644
--- a/configs/nios2-generic_defconfig
+++ b/configs/nios2-generic_defconfig
@@ -1,9 +1,12 @@
 CONFIG_NIOS2=y
 CONFIG_TARGET_NIOS2_GENERIC=y
+CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_BOOTD is not set
 # CONFIG_CMD_IMLS is not set
 # 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