Fix warning differ in signedness in net/net.c and net/nfs.c
diff --git a/net/bootp.c b/net/bootp.c
index 55dcc81..89e30d2 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -33,7 +33,7 @@
 
 #if defined(CONFIG_CMD_NET)
 
-#define TIMEOUT		5		/* Seconds before trying BOOTP again	*/
+#define TIMEOUT		5UL		/* Seconds before trying BOOTP again	*/
 #ifndef CONFIG_NET_RETRY_COUNT
 # define TIMEOUT_COUNT	5		/* # of timeouts before giving up  */
 #else