leds: is31fl319x: Make use of device properties

Convert the module to be property provider agnostic and allow
it to be used on non-OF platforms.

Add mod_devicetable.h include.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Vincent Knecht <vincent.knecht@mailoo.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>