dt-bindings: leds: Add ROHM BD2606MVV LED

Document ROHM BD2606MVV LED driver devicetree bindings.

Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230419111806.1100437-2-andreas@kemnade.info