Fix warning differ in signedness in net/net.c and net/nfs.c
diff --git a/net/rarp.c b/net/rarp.c
index 21dfa52..ecf38e4 100644
--- a/net/rarp.c
+++ b/net/rarp.c
@@ -31,7 +31,7 @@
 
 #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