HID: fixed bug in single-touch emulation on the stantum panel

Fixed stupid copy-paste bug in touchscreen emulation for the Stantum multitouch
panel: a flag was reset just before being tested.

Signed-off-by: Stephane Chatty <chatty@enac.fr>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>