leds: leds-mc13783: Remove duplicate field in platform data

LED platform data are overwhelmed by excessive field "max_cur"
which just replicates few bits of "led_control" field.
This patch removes this field and adds a definition for the
current settings in the header.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Bryan Wu <cooloney@gmail.com>