cmd: zip: use correct format code

dst_len is defined as unsigned long. So use %lu for printf().

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/cmd/zip.c b/cmd/zip.c
index d105d84..9cd400a 100644
--- a/cmd/zip.c
+++ b/cmd/zip.c
@@ -28,7 +28,7 @@
 	if (gzip((void *) dst, &dst_len, (void *) src, src_len) != 0)
 		return 1;
 
-	printf("Compressed size: %ld = 0x%lX\n", dst_len, dst_len);
+	printf("Compressed size: %lu = 0x%lX\n", dst_len, dst_len);
 	env_set_hex("filesize", dst_len);
 
 	return 0;