i2c-i801: Restore the device state before leaving

Restore the original host configuration on driver unload and on
suspend. In particular this returns the SMBus master in I2C mode if it
was originally in I2C mode, which should help with suspend/resume if
the BIOS expects to find the SMBus master in I2C mode.

This fixes bug #6449 (for real this time.)
http://bugzilla.kernel.org/show_bug.cgi?id=6449



Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Tommi Kyntola <tommi.kyntola@ray.fi>