arm: kirkwood: Move configuration of some commands to _defconfig files

For Marvell plugs, move the configuration of DHCP, NAND/SF, PING
and USB commands, and HUSH_PARSER into the _defconfig file, rather
than the include/configs/*plug.h files.

This avoids compiler warnings of duplicate definitions if the
option is selected in the .config, but also defined in the
include/configs/*plug.h file.

Signed-off-by: Quentin Armitage <quentin@armitage.org.uk>
diff --git a/configs/dreamplug_defconfig b/configs/dreamplug_defconfig
index 501fbbf..ec2a749 100644
--- a/configs/dreamplug_defconfig
+++ b/configs/dreamplug_defconfig
@@ -5,3 +5,8 @@
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_SPI_FLASH=y
+CONFIG_HUSH_PARSER=y
+CONFIG_CMD_DHCP=y
+CONFIG_CMD_SF=y
+CONFIG_CMD_PING=y
+CONFIG_CMD_USB=y