clk: sunxi-ng: Use a separate lock for each CCU instance

Some platforms have more than one CCU driver loaded: the main CCU, the
PRCM, the display engine, and possibly others. All of these hardware
blocks have separate MMIO spaces, so there is no need to synchronize
between them.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210901050526.45673-4-samuel@sholland.org