Update to kernel headers v4.12.3.

Test: Built angler.
Change-Id: Icbcf4fac2334de8409b049ed7a3b4c24b4e98ce9
diff --git a/libc/kernel/uapi/linux/ipv6.h b/libc/kernel/uapi/linux/ipv6.h
index 125657c..d07fa06 100644
--- a/libc/kernel/uapi/linux/ipv6.h
+++ b/libc/kernel/uapi/linux/ipv6.h
@@ -137,6 +137,9 @@
   DEVCONF_SEG6_ENABLED,
   DEVCONF_SEG6_REQUIRE_HMAC,
   DEVCONF_ENHANCED_DAD,
+  DEVCONF_ADDR_GEN_MODE,
+  DEVCONF_DISABLE_POLICY,
+  DEVCONF_ACCEPT_RA_RT_INFO_MIN_PLEN,
   DEVCONF_MAX
 };
 #endif