MIPS: Add CPU support for Loongson1C

Loongson1C is a 32-bit SoC designed by Loongson Technology Co., Ltd,
with many features similar to Loongson1B.

Signed-off-by: Yang Ling <gnaygnil@gmail.com>
Cc: paul.burton@imgtec.com
Cc: markos.chandras@imgtec.com
Cc: james.hogan@imgtec.com
Cc: kumba@gentoo.org
Cc: macro@imgtec.com
Cc: david.daney@cavium.com
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13303/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>