riscv: defconfig: spacemit: k3: enable clock support

Enable the clock driver support for SpacemiT K3 SoC, configure it as
built-in by default, but users should be able to change it as kernel
module if needed.

Signed-off-by: Yixun Lan <dlan@kernel.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>