dt-bindings: clock: sun8i-de2: Add H6 DE3 clock description

This commit adds necessary description and dt includes for H6 DE3 clock.
It is very similar to others, but memory region has some additional
registers not found in DE2.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>