clk: sunxi-ng: Add A80 CCU

Add support for the main clock unit found in the A80. Some clocks were
not documented in the released user manual, but were found in the
official kernel from Allwinner. These include controls for the I2S,
SPDIF, SATA, and eDP blocks.

Note that on the A80, some subsystems have separate clock controllers
downstream of the main clock unit. These include the MMC, USB, and
display engine subsystems.

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