clk: clk-loongson2: Add Loongson-2K2000 clock support

The Loongson-2K2000 and Loongson-2K1000 clock is similar, we add its
support by different configurations.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Link: https://lore.kernel.org/r/8b0b5851783acf8ebe13b50391d15b58cc181613.1712731524.git.zhoubinbin@loongson.cn
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>