leds: lm3692x: Don't overwrite return value in error path

The driver currently reports successful initialization on every failure
as long as it's able to power off the regulator. Don't check the return
value of regulator_disable to avoid that.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>