MIPS: Loongson 1B: Add defconfig

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: wuzhangjin@gmail.com
Cc: zhzhl555@gmail.com
Cc: Kelvin Cheung <keguang.zhang@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/4135/


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