Connect up the sysarch system call.

Signed-off-by: Juergen Lock <nox@jelal.kn-bremen.de>
Co-authored-by: Juergen Lock <nox@jelal.kn-bremen.de>
Signed-off-by: Stacey Son <sson@FreeBSD.org>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>