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/ila.h b/libc/kernel/uapi/linux/ila.h
index a5af23a..75de8eb 100644
--- a/libc/kernel/uapi/linux/ila.h
+++ b/libc/kernel/uapi/linux/ila.h
@@ -39,6 +39,7 @@
   ILA_CMD_ADD,
   ILA_CMD_DEL,
   ILA_CMD_GET,
+  ILA_CMD_FLUSH,
   __ILA_CMD_MAX,
 };
 #define ILA_CMD_MAX (__ILA_CMD_MAX - 1)