can: softing: softing_netdev_open(): remove redundant ret variable

Return value from softing_startstop() directly instead of taking this
in another redundant variable.

Link: https://lore.kernel.org/all/20220112080629.667191-1-chi.minghao@zte.com.cn


Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Signed-off-by: CGEL ZTE <cgel.zte@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>