* update to commit 163ba35f ("doc: use KCFLAGS instead of
  EXTRA_CFLAGS to pass flags from command line")
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/Ywli7VfhQVPHKiGw@bobwxc.mipcSigned-off-by: Jonathan Corbet <corbet@lwn.net>