clk: spacemit: Add clock support for SpacemiT K1 SoC

The clock tree of K1 SoC contains three main types of clock hardware
(PLL/DDN/MIX) and has control registers split into several multifunction
devices: APBS (PLLs), MPMU, APBC and APMU.

All register operations are done through regmap to ensure atomicity
between concurrent operations of clock driver and reset,
power-domain driver that will be introduced in the future.

Signed-off-by: Haylen Chu <heylenay@4d2.org>
Reviewed-by: Alex Elder <elder@riscstar.com>
Reviewed-by: Inochi Amaoto <inochiama@outlook.com>
Reviewed-by: Yixun Lan <dlan@gentoo.org>
Link: https://lore.kernel.org/r/20250416135406.16284-4-heylenay@4d2.org


Signed-off-by: Yixun Lan <dlan@gentoo.org>