leds-lp55xx: use lp55xx common init function - detect

 LP5521/5523 chip detection functions are replaced with lp55xx common function,
 lp55xx_detect_device().
 Chip dependent address and values are configurable in each driver.
 In init function, chip detection is executed.

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