leds: pca9532: fix a potential NULL pointer dereference

In case of_match_device cannot find a match, return -EINVAL to avoid
NULL pointer dereference.

Fixes: fa4191a6

 ("leds: pca9532: Add device tree support")
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>