fix ALPHA
fix ALPHA

cpu/exec_context.cc:
    put this code between #ifdef FULL_SYSTEM

LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,haowu4682/gem5,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,LingxiaoJIA/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5