Update to v4.19 kernel headers.

Test: Builds and boots.
Change-Id: I99a9ed79666e143b47f02ca4e59eed94f69b7e4a
(cherry picked from commit a981e2e52e2e95a65fa9c9b6fb16dcb4c83dd576)
diff --git a/libc/kernel/uapi/linux/if_addr.h b/libc/kernel/uapi/linux/if_addr.h
index cefc11b..0a4b0ae 100644
--- a/libc/kernel/uapi/linux/if_addr.h
+++ b/libc/kernel/uapi/linux/if_addr.h
@@ -37,6 +37,7 @@
   IFA_CACHEINFO,
   IFA_MULTICAST,
   IFA_FLAGS,
+  IFA_RT_PRIORITY,
   __IFA_MAX,
 };
 #define IFA_MAX (__IFA_MAX - 1)