staging: unisys: add visorhid driver

This driver provides mouse and keyboard input to Unisys s-Par
Partition Desktop application. This device is created by the
visorbus device.

Signed-off-by: Erik Arfvidson <erik.arfvidson@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Tim Sell <timothy.sell@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>