leds: leds-mt6323: Add support for MT6331 leds

Add the register offsets for MT6331. The hwspec is the same as MT6323.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230601110813.2373764-8-angelogioacchino.delregno@collabora.com