MIPS: Loongson32: clarify we don't support MIPS16 and merge configs

Accorading to GS232 core user's manual, it doesn't support MIPS16.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: keguang.zhang@gmail.com