leds-bcm6328: add more init configuration options

This patch adds more init register configuration options:
- Serial LEDs multiplexing.
- Serial LEDs clock signal low/high polarity.
- Serial LEDs data signal low/high polarity.
- Serial LEDs shift direction inverted/normal.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>