clk: sunxi: Add Kconfig options

We used to have a clock framework that isn't really used these days, except
for a few clocks and/or SoCs. Most of the time, the new framework and
drivers (sunxi-ng) will provide everything needed for the customer devices
to operate properly.

Since we're not needing it that much, it might make sense to disable those
drivers, for example when we want to reduce the kernel size. Let's add
options in Kconfig that can be disabled if needed, but are still on by
default to keep the same features in the standard case.

Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>