drivers: led: lp503x: extend driver to all lp50xx devices

Add support for LP5009, LP5012, LP5018 and LP5024 devices which only
differ by the number of LEDs they can control.

Also, update application sample to run on all these new supported
devices.

Based on initial work from:
  - Marek Janus <marek.janus@grinn-global.com>
  - Rico Ganahl <rico.ganahl@bytesatwork.ch>

Signed-off-by: Mathieu Anquetin <mathieu.anquetin@groupe-cahors.com>