led: triggers: Break the for loop after default trigger is found

It is of no avail to continue iterating through registered
triggers in the led_trigger_set_default() after the trigger to set
has been found. Add "break" statement to fix this omission.

Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>