Input: usbtouchscreen - actually check return value of usb_submit_urb()

Fixes the following W=1 kernel build warning(s):

 drivers/input/touchscreen/usbtouchscreen.c: In function ‘nexio_read_data’:
 drivers/input/touchscreen/usbtouchscreen.c:1052:50: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20210114152323.2382283-4-lee.jones@linaro.org


[dtor: log error code as well]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>