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

Commit 51003b89 attempted to fix a build problem on 64 bit systems,
but just turned it into a build problem on 32 bit systems (silly me).

Now do the Right Thing (TM) and use a "%zu" printf format.

Also fix spelling error.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index ee067cb..7b26920 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 %ld\n",
+		printf ("Error:%s[%d] - length is not in multiple of %zu\n",
 			__FUNCTION__, len, sizeof(uint32_t));
 		return 0;
 	}