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/arch/arm/Kconfig b/arch/arm/Kconfig
index b828b8d..7264d72 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2052,6 +2052,14 @@
 	  image headers.
 endif
 
+config SYS_KWD_CONFIG
+	string "kwbimage config file path"
+	depends on ARCH_KIRKWOOD || ARCH_MVEBU
+	default "arch/arm/mach-mvebu/kwbimage.cfg"
+	help
+	  Path within the source directory to the kwbimage.cfg file to use
+	  when packaging the U-Boot image for use.
+
 source "arch/arm/mach-apple/Kconfig"
 
 source "arch/arm/mach-aspeed/Kconfig"