kwbimage.c: Fix compile warning when building on 64 bit systems

Fix this warning when building on 64 bit systems:
tools/kwbimage.c: In function 'kwbimage_checksum32':
tools/kwbimage.c:135: warning: format '%d' expects type 'int',
but argument 4 has type 'long unsigned int'

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Prafulla Wadaskar <prafulla@marvell.com>
diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index 28dc2d6..ee067cb 100644
--- a/tools/kwbimage.c
+++ b/tools/kwbimage.c
@@ -131,7 +131,7 @@
 		return 0;
 
 	if (len % sizeof(uint32_t)) {
-		printf ("Error:%s[%d] - lenght is not in multiple of %d\n",
+		printf ("Error:%s[%d] - lenght is not in multiple of %ld\n",
 			__FUNCTION__, len, sizeof(uint32_t));
 		return 0;
 	}