MIPS: Loongson: Fix GENMASK misuse

Arguments are supposed to be ordered high then low.

Fixes: 6a6f9b7d ("MIPS: Loongson: Add CFUCFG&CSR support")
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Reviewed-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: chenhuacai@gmail.com
Cc: jhogan@kernel.org
Cc: jiaxun.yang@flygoat.com
Cc: linux-mips@linux-mips.org
Cc: linux-mips@vger.kernel.org
Cc: paul.burton@mips.com
Cc: ralf@linux-mips.org
Cc: wuzhangjin@gmail.com
Cc: zhangfx@lemote.com