pch_phub: Support new device LAPIS Semiconductor ML7831 IOH

ML7831 is companion chip for Intel Atom E6xx series.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.lapis-semi.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>