HID: add multi-input quirk for IDC6680 touchscreen

The Ideacom 6680 touchscreen is found in the Dell Latitude 2100. It
has two USB descriptors, the first of which has two input reports. The
HID_QUIRK_MULTI_INPUT quirk is needed to keep the correct maximum
value for ABS_X/ABS_Y (8191 instead of 65535).

Signed-off-by: Nicholas Bishop <nbishop@neverware.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>