leds-lp55xx: use lp55xx common init function - reset

 LP5521/5523 reset device functions are moved to lp55xx common driver.
 Value of register address and value are chip dependent.
 Those are configured in each driver.
 In init function, reset command is executed.

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