kirkwood: kwbimage: refactor CONFIG_SYS_KWD_CONFIG

Pull out "$(SRCTREE)/" from CONFIG_SYS_KWD_CONFIG
and push it into the top Makefile.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Michael Walle <michael@walle.cc>
Cc: Simon Guinot <simon.guinot@sequanux.org>
Cc: Dave Purdy <david.c.purdy@gmail.com>
Cc: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>
Cc: Luka Perkov <luka@openwrt.org>
Cc: Valentin Longchamp <valentin.longchamp@keymile.com>
Cc: Jason Cooper <u-boot@lakedaemon.net>
Cc: Siddarth Gore <gores@marvell.com>
Cc: Prafulla Wadaskar <prafulla@marvell.com>
Cc: Eric Cooper <ecc@cmu.edu>
Cc: Suriyan Ramasami <suriyan.r@gmail.com>
diff --git a/include/configs/lsxl.h b/include/configs/lsxl.h
index 92865df..2ae8a27 100644
--- a/include/configs/lsxl.h
+++ b/include/configs/lsxl.h
@@ -13,12 +13,12 @@
  */
 #if defined(CONFIG_LSCHLV2)
 #define CONFIG_IDENT_STRING " LS-CHLv2"
-#define CONFIG_SYS_KWD_CONFIG $(SRCTREE)/$(CONFIG_BOARDDIR)/kwbimage-lschl.cfg
+#define CONFIG_SYS_KWD_CONFIG $(CONFIG_BOARDDIR)/kwbimage-lschl.cfg
 #define CONFIG_MACH_TYPE 3006
 #define CONFIG_SYS_TCLK 166666667 /* 166 MHz */
 #elif defined(CONFIG_LSXHL)
 #define CONFIG_IDENT_STRING " LS-XHL"
-#define CONFIG_SYS_KWD_CONFIG $(SRCTREE)/$(CONFIG_BOARDDIR)/kwbimage-lsxhl.cfg
+#define CONFIG_SYS_KWD_CONFIG $(CONFIG_BOARDDIR)/kwbimage-lsxhl.cfg
 #define CONFIG_MACH_TYPE 2663
 /* CONFIG_SYS_TCLK is 200000000 by default */
 #else