HID: wacom: Report 'strip2' values in ABS_RY

Commit c7f0522a accidentally used ABS_RX for reporting both 'strip1' and
'strip2', when the latter should actually be reported through ABS_RY.

Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>