HID: hid-multitouch: support for PixCir-based panels

Created a driver for PixCir based dual-touch panels, including the one
in the Hanvon tablet.  This is done in a code structure aimed at unifying
support for several existing HID multitouch panels.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Signed-off-by: Stéphane Chatty <chatty@enac.fr>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>