clk: Add Sunplus SP7021 clock driver

Add clock driver for Sunplus SP7021 SoC.

Signed-off-by: Qin Jian <qinjian@cqplus1.com>
Link: https://lore.kernel.org/r/20221219015130.42621-1-qinjian@cqplus1.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>