udhcpc: do not use -t NUM for counting "select" packets, use 3

Otherwise, "-t 0" usage may end up sending them forever
if server does not respond.

function                                             old     new   delta
udhcpc_main                                         2846    2836     -10

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 6c2b112..dfd5ca6 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1501,7 +1501,7 @@
 				packet_num = 0;
 				continue;
 			case REQUESTING:
-				if (!discover_retries || packet_num < discover_retries) {
+				if (packet_num < 3) {
 					/* send broadcast select packet */
 					send_select(xid, server_addr, requested_ip);
 					timeout = discover_timeout;