leds: led-triggers: Fix checkpatch warnings

Fixes the following type of warnings:
WARNING: Prefer netdev_warn(netdev, ... then dev_warn(dev, ...
then pr_warn(...  to printk(KERN_WARNING ...
WARNING: quoted string split across lines

While at it also fix a coding style issue w.r.t braces.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Bryan Wu <cooloney@gmail.com>