Input: xpad - add support for Xbox 360 gamepad

Xbox 360 gamepad is slightly different then the previous model so it has
its own version of process_packet method. Detection of this new device
relies on USB_DEVICE_INTERFACE_PROTOCOL macro. This device got vendor
specific subclass so it can't be matched with USB_INTERFACE_INFO and
we need only one interface protocol from four availaible. It means
USB_DEVICE can't be used either.

Added xpad360_btn structure with additional buttons for x360 gamepad.
Added xtype into xpad_device structure to distinguish between different
types of xbox devices.

Signed-off-by: Jan Kratochvil <honza@jikos.cz>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>