clk: sunxi-ng: Add A23 CCU

Add support for the clock unit found in the A23. Due to the similarities
with the A33, it also shares its clock IDs to allow sharing the DTSI.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>