x86/head64: Remove duplicate include

Remove duplicate header include.

Signed-off-by: Wang Qing <wangqing@vivo.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1604893542-20961-1-git-send-email-wangqing@vivo.com