Fix bad padding of bootp request packet

This seems to pad to one byte longer than required

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/net/bootp.c b/net/bootp.c
index 1a71786..87b027e 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -464,7 +464,7 @@
 
 	/* Pad to minimal length */
 #ifdef	CONFIG_DHCP_MIN_EXT_LEN
-	while ((e - start) <= CONFIG_DHCP_MIN_EXT_LEN)
+	while ((e - start) < CONFIG_DHCP_MIN_EXT_LEN)
 		*e++ = 0;
 #endif