media: i2c: tc358746: fix missing return assignment

It was intended to return an error if tc358746_update_bits() call fail.
Fix this by storing the return code.

Addresses-Coverity-ID: 1527252 ("Control flow issues")

Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
Fixes: 80a21da3 ("media: tc358746: add Toshiba TC358746 Parallel to CSI-2 bridge driver")
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>