<netinet/ip_icmp.h>: ensure struct icmphdr is available.

Needed to build toybox ping.

Bug: N/A
Test: ran tests
Change-Id: Ifd0f0ccbb8351c6a0ece526b050778fd02e984bf
diff --git a/libc/include/netinet/ip_icmp.h b/libc/include/netinet/ip_icmp.h
index 7510592..d6f89bc 100644
--- a/libc/include/netinet/ip_icmp.h
+++ b/libc/include/netinet/ip_icmp.h
@@ -35,9 +35,11 @@
 #ifndef _NETINET_IP_ICMP_H_
 #define _NETINET_IP_ICMP_H_
 
-#include <netinet/ip.h>
 #include <sys/cdefs.h>
 
+#include <linux/icmp.h>
+#include <netinet/ip.h>
+
 __BEGIN_DECLS
 
 /*