Input: wacom - fix error return code in wacom_probe()

Fix to return a negative error code from the urb submit error
handling case instead of 0, as done elsewhere in this function.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>