This patch adds support for creation heartbeat led trigger with,
for example, this command:
ucidef_set_led_heartbeat "..." "..." "..."
from /etc/board.d/01_leds.
Signed-off-by: Alexey Smirnov <s.alexey@gmail.com>
(cherry picked from commit 66071729a27919e555752fce25210b1b035eb319)
1ea34b9621