target/loongarch: Fix raise_mmu_exception() set wrong exception_index

target/loongarch: Fix raise_mmu_exception() set wrong exception_index

When the address is invalid address, We should set exception_index
according to MMUAccessType, and EXCCODE_ADEF need't update badinstr.
Otherwise, The system enters an infinite loop. e.g:
run test.c on system mode
test.c:
    #include<stdio.h>

    void (*func)(int *);

    int main()
    {
        int i = 8;
        void *ptr = (void *)0x4000000000000000;
        func = ptr;
        func(&i);
        return 0;
    }

Signed-off-by: Song Gao <gaosong@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20221101073210.3934280-2-gaosong@loongson.cn>