dt-bindings: as3645a: Add function and color properties

Refer to new "function" and "color" properties and mark "label"
as deprecated.

Also, fix malformed syntax of address-cells and size-cells
in the example.

Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Rob Herring <robh@kernel.org>