Back out part of last change

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1619 42af7a65-404d-4744-a932-0658087f49c3

net/uip/uip_chksum.c

@@ -229,7 +229,7 @@ uint16 uip_udpchksum(struct uip_driver_s *dev)
 
 /* Calculate the checksum of the ICMP message */
 
-#if defined(CONFIG_NET_ICMP)
+#if defined(CONFIG_NET_ICMP) && defined(CONFIG_NET_ICMP_PING)
 uint16 uip_icmpchksum(struct uip_driver_s *dev, int len)
 {
   struct uip_icmpip_hdr *picmp = ICMPBUF;