Input: usbtouchscreen - add support for e2i touchscreen controller

This patch adds support for the e2i touchscreen controller used in the
Mimo 740 (and probably in other e2i touchscreen products). Tested on
Mimo 740.

Signed-off-by: Florian Echtler <floe@butterbrot.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>