ping: use ICMP_MINLEN

no code changes

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
diff --git a/networking/ping.c b/networking/ping.c
index 4e770bd..23b39f2 100644
--- a/networking/ping.c
+++ b/networking/ping.c
@@ -162,7 +162,7 @@
 				bb_perror_msg("recvfrom");
 			continue;
 		}
-		if (c >= 8) {			/* icmp6_hdr */
+		if (c >= ICMP_MINLEN) {			/* icmp6_hdr */
 			pkt = (struct icmp6_hdr *) packet;
 			if (pkt->icmp6_type == ICMP6_ECHO_REPLY)
 				break;