Input: usbtouchscreen - add support for LG Flatron T1710B

I've recently got my hands on a LG Flatron T1710B touchscreen.
As other LG products, this seems to use the ITM panel.

Signed-off-by: Glenn Sommer <gsommer@datanordisk.dk>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>