leds: lp50xx: Remove duplicated error reporting in .remove()

Returning an error value from an i2c remove callback results in an error
message being emitted by the i2c core, but otherwise it doesn't make a
difference. The device goes away anyhow and the devm cleanups are
called.

As stk3310_set_state() already emits an error message on failure and the
additional error message by the i2c core doesn't add any useful
information, don't pass the error value up the stack. Instead continue
to clean up and return 0.

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: Pavel Machek <pavel@ucw.cz>