leds: tlc591xx: merge conditional tests

Merge conditionals that have the same then branch, to prepare for extending
that branch with of_node_put.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>