clk: sunxi-ng: Add support for the Allwinner H616 CCU

While the clocks are fairly similar to the H6, many differ in tiny
details, so a separate clock driver seems indicated.

Derived from the H6 clock driver, and adjusted according to the manual.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210127172500.13356-4-andre.przywara@arm.com