clk: sunxi-ng: Allow drivers to be built as modules

While it is useful to build all of the CCU drivers at once, only 1-3 of
them will be loaded at a time, or possibly none of them if the kernel is
booted on a non-sunxi platform. These CCU drivers are relatively large;
32-bit drivers have 30-50k of data each, while the 64-bit ones are
50-75k due to the increased pointer overhead. About half of that data
comes from relocations. Let's allow the user to build these drivers as
modules so only the necessary data is loaded.

As a first step, convert the CCUs that are already platform drivers.

When the drivers are built as modules, normally the file name becomes
the module name. However, the current file names are inconsistent with
the <platform>-<peripheral> name used everywhere else: the devicetree
bindings, the platform driver names, and the Kconfig symbols. Use
Makfile logic to rename the modules so they follow the usual pattern.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20211119033338.25486-3-samuel@sholland.org