clk: spacemit: Respect Kconfig setting when building modules

clk: spacemit: Respect Kconfig setting when building modules

Currently, the SPACEMIT_CCU entry is only a switch for enabling entry
SPACEMIT_K1_CCU. It does not guide the build for common clock codes
even if it is a tristate entry. This makes this entry useless.

Change the Makefile to add a separate build for common clock logic,
so the SPACEMIT_CCU entry takes effect, also add necessary
MODULE_LICENSE()/MODULE_DESCRIPTION()/EXPORT_SYMBOL() for the module
build.

Fixes: 1b72c59db0ad ("clk: spacemit: Add clock support for SpacemiT K1 SoC")
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Reviewed-by: Yixun Lan <dlan@gentoo.org>
Link: https://lore.kernel.org/r/20251219012819.440972-2-inochiama@gmail.com
Signed-off-by: Yixun Lan <dlan@gentoo.org>