can: softing_cs: ret is never non-zero, so remove non-zero check and -ENODEV return

The error return ret is never zero in the error handling path in
softingcs_probe, so the check for non-zero and returning -ENODEV
is logically dead code and hence redundant.  Remove it and just
return ret.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>