leds: leds-mt6323: Specify registers and specs in platform data

In order to enhance the flexibility of this driver and let it support
more than just one MediaTek LEDs IP for more than just one PMIC,
add platform data structure specifying the register offsets and
data that commonly varies between different IPs.

This commit brings no functional changes.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230601110813.2373764-5-angelogioacchino.delregno@collabora.com