HID: wacom: bits shifted too much for 9th and 10th buttons

Cintiq 12 has 10 expresskey buttons. The bit shift for the last
two buttons were off by 5.

Fixes: c7f0522a ("HID: wacom: Slim down wacom_intuos_pad processing")

Signed-off-by: Ping Cheng <ping.cheng@wacom.com>
Tested-by: Matthieu Robin <matthieu@macolu.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>