dt-bindings: leds: common: fix unit address in max77693 example

The max77693 LED device node should not take an unit address, because it
is instantiated from a max77693 I2C parent device node.  This also
splits all examples to separate DTS examples because they are actually
independent.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>