net: Fix compile errors when SNTP enabled and not DATE

When SNTP is enabled and DATE is not, to_tm() is not built in. It could
be defined when TIMESTAMP is defined, so check for that.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/net/sntp.c b/net/sntp.c
index d3427d8..6422eef 100644
--- a/net/sntp.c
+++ b/net/sntp.c
@@ -50,17 +50,20 @@
 static void sntp_handler(uchar *pkt, unsigned dest, struct in_addr sip,
 			 unsigned src, unsigned len)
 {
+#ifdef CONFIG_TIMESTAMP
 	struct sntp_pkt_t *rpktp = (struct sntp_pkt_t *)pkt;
 	struct rtc_time tm;
 	ulong seconds;
+#endif
 
 	debug("%s\n", __func__);
 
 	if (dest != sntp_our_port)
 		return;
 
+#ifdef CONFIG_TIMESTAMP
 	/*
-	 * As the RTC's used in U-Boot sepport second resolution only
+	 * As the RTC's used in U-Boot support second resolution only
 	 * we simply ignore the sub-second field.
 	 */
 	memcpy(&seconds, &rpktp->transmit_timestamp, sizeof(ulong));
@@ -72,6 +75,7 @@
 	printf("Date: %4d-%02d-%02d Time: %2d:%02d:%02d\n",
 	       tm.tm_year, tm.tm_mon, tm.tm_mday,
 	       tm.tm_hour, tm.tm_min, tm.tm_sec);
+#endif
 
 	net_set_state(NETLOOP_SUCCESS);
 }