tcg/mips: Bugfix for crash when running program with qemu-i386.

When running a helloworld program with qemu-i386 in linux-user
mode on Loongson 3A3000, it will crash. This patch fix the bug.

Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn>
Message-Id: <1499669979-25904-1-git-send-email-jiang.biao2@zte.com.cn>
Signed-off-by: Richard Henderson <rth@twiddle.net>