Input: usbtouchscreen - add support for IRTOUCHSYSTEMS touchscreens

This patch adds support for IRTOUCHSYSTEMS (or UNITOP) infrared touchscreens.

The touchscreen sends data in 8-byte packets.
BYTE 0 - unknown meaning, seen only one value: 0x54
BYTE 1 - unknown meaning, 3 lowest bits indicate touch state
        values seen: 0x81, 0x82 or 0x83
        bit 0 = set if the screen is touched and was not touched before (touch
        bit 1 = set if the screen is touched and was touched (dragging)
        bit 2 = set if the touch was ended (release)
BYTES 2 and 3 - X position, high-order-byte first, range = 0 to 0x0FFF
BYTES 4 and 5 - Y position, high-order-byte first, range = 0 to 0x0FFF
BYTE 6 - unknown meaning, seen only one value: 0xFF
BYTE 7 - unknown meaning, seen only one value: 0x00

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Daniel Ritz <daniel.ritz@gmx.ch>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>