can: gs_usb: gs_usb_probe(): use descriptors of current altsetting

commit 2f361cd9474ab2c4ab9ac8db20faf81e66c6279b upstream.

Make sure to always use the descriptors of the current alternate setting
to avoid future issues when accessing fields that may differ between
settings.

Signed-off-by: Johan Hovold <johan@kernel.org>
Fixes: d08e973a ("can: gs_usb: Added support for the GS_USB CAN devices")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>