The only effect of returning an error code in an i2c remove callback is
that the i2c core emits a generic warning and still removes the device.

So even if disabling the regulator fails it's sensible to further cleanup
and then return zero to only emit a single error message.

This patch is a preparation for making i2c remove callbacks return void.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>