Input: usbtouchscreen - implement reset_resume

This implements reset_resume() by splitting init into allocations
of private data structures and device initializations. Device
initializations are repeated upon reset_resume.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Tested-by: Petr Štetiar <ynezz@true.cz>
Tested-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>