leds-lp5523: turn off the LED engines on unloading the driver

The LP5523 has 3 engines which are used for running LED patterns.
These engines should be off while unloading the driver.
Obviously, LP5523 platform data are used for releasing the resource
such like enable()/release_resource(), but these are not mandatory.
Therefore this patch is required without the platform data dependency.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>