GS232 core used in Loongson-1 processors has a bug that
di instruction doesn't save the irqflag immediately.

Workaround by set irqflag in CP0 before di instructions
as same as Loongson-3.
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