Convert CONFIG_SYS_KWD_CONFIG to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_KWD_CONFIG

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/guruplug_defconfig b/configs/guruplug_defconfig
index 2e6b8e0..e7802af 100644
--- a/configs/guruplug_defconfig
+++ b/configs/guruplug_defconfig
@@ -3,6 +3,7 @@
 CONFIG_SYS_DCACHE_OFF=y
 CONFIG_ARCH_CPU_INIT=y
 CONFIG_ARCH_KIRKWOOD=y
+CONFIG_SYS_KWD_CONFIG="board/Marvell/guruplug/kwbimage.cfg"
 CONFIG_SYS_TEXT_BASE=0x600000
 CONFIG_NR_DRAM_BANKS=2
 CONFIG_TARGET_GURUPLUG=y