leds: max5970: 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>
Link: https://lore.kernel.org/r/20231214184050.1272848-3-andriy.shevchenko@linux.intel.com


Signed-off-by: Lee Jones <lee@kernel.org>