LoongArch: dts: Add PWM support to Loongson-2K1000

The module is supported, enable it.

Also, add the pwm-fan and cooling-maps associated with it.

Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>