leds-lp55xx: use common lp55xx data structure in _probe()

 LP5521 and LP5523 data structures have common features.
 Use common lp55xx data structures rather than chip specific data.
 Legacy code in probe is replaced with this new data structures.

 lp55xx_chip          : Common data between lp5521_chip and lp5523_chip
 lp55xx_led           : Common LED structure between lp5521_led and lp5523_led
 lp55xx_platform_data : Common platform data between lp5521_platform_data and
                        lp5523_platform_data

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