leds: lp8860: Add regulator enable during init

Add the regulator enable call during initialization.
If init fails then disable the regulator.

Also during init the gpio gets set low even
on a passing case so add if everything passes
then return.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
