Support new device OKI SEMICONDUCTOR ML7831 IOH(Input/Output Hub)

ML7831 is for general purpose use.
ML7831 is companion chip for Intel Atom E6xx series.
ML7831 is completely compatible for Intel EG20T PCH.
Signed-off-by: NToshiharu Okada <toshiharu-linux@dsn.okisemi.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>