leds: lm3532: Switch to use fwnode_property_count_uXX()

Use fwnode_property_count_uXX() directly, that makes code neater.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>