leds: pca963x: register LEDs immediately after parsing, get rid of platdata

Register LEDs immediately after parsing their properties.
This allows us to get rid of platdata, and since no one in tree uses
header linux/platform_data/leds-pca963x.h, remove it.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: Peter Meerwald <p.meerwald@bct-electronic.com>
Cc: Ricardo Ribalda <ribalda@kernel.org>
Cc: Zahari Petkov <zahari@balena.io>
Signed-off-by: Pavel Machek <pavel@ucw.cz>