leds-lp55xx: replace name of data structure

 Change the name of chip data structure and platform data.
 This patch is a preceding step for cleaning up lp5521/5523 probe and remove.
 These data will be replaced with new lp55xx common data structures
 in next patch.

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