HID: wacom: add missed stylus_in_proximity line back

Commit 7e129783 ("HID: wacom: break out wacom_intuos_get_tool_type") by accident
removed stylus_in_proximity flag for Intuos series while shuffling the code
around.

Fix that by reintroducing that flag setting in wacom_intuos_inout(), where
it originally was.

Fixes: 7e129783

 ("HID: wacom: break out wacom_intuos_get_tool_type")
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>