dt-bindings: soc: spacemit: Add spacemit,k1-syscon

dt-bindings: soc: spacemit: Add spacemit,k1-syscon

Document APMU, MPMU and APBC syscons found on SpacemiT K1 SoC, which are
capable of generating clock and reset signals. Additionally, APMU and MPMU
manage power domains.

Signed-off-by: Haylen Chu <heylenay@4d2.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Alex Elder <elder@riscstar.com>
Reviewed-by: Yixun Lan <dlan@gentoo.org>
Link: https://lore.kernel.org/r/20250416135406.16284-2-heylenay@4d2.org
Signed-off-by: Yixun Lan <dlan@gentoo.org>