Update to v4.17.3 kernel headers.

Test: Builds, boots on a walleye.
Change-Id: I389d8b61ec00ea309e38d1b1a2e0dace48c21edb
diff --git a/libc/kernel/uapi/linux/if_tunnel.h b/libc/kernel/uapi/linux/if_tunnel.h
index 8edc956..d41dc49 100644
--- a/libc/kernel/uapi/linux/if_tunnel.h
+++ b/libc/kernel/uapi/linux/if_tunnel.h
@@ -136,6 +136,9 @@
   IFLA_GRE_IGNORE_DF,
   IFLA_GRE_FWMARK,
   IFLA_GRE_ERSPAN_INDEX,
+  IFLA_GRE_ERSPAN_VER,
+  IFLA_GRE_ERSPAN_DIR,
+  IFLA_GRE_ERSPAN_HWID,
   __IFLA_GRE_MAX,
 };
 #define IFLA_GRE_MAX (__IFLA_GRE_MAX - 1)