tcg/i386: Check the size of instruction being translated

This fixes the bug: 'user-to-root privesc inside VM via bad translation
caching' reported by Jann Horn here:
https://bugs.chromium.org/p/project-zero/issues/detail?id=1122

Reviewed-by: Richard Henderson <rth@twiddle.net>
CC: Peter Maydell <peter.maydell@linaro.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Message-Id: <20170323175851.14342-1-bobby.prani@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static inline void gen_op_movq(int d_offset, int s_offset)
{
    tcg_gen_ld_i64(cpu_tmp1_i64, cpu_env, s_offset);
    tcg_gen_st_i64(cpu_tmp1_i64, cpu_env, d_offset);
}

static inline void gen_op_movq(int d_offset, int s_offset)
{
    tcg_gen_ld_i64(cpu_tmp1_i64, cpu_env, s_offset);
    tcg_gen_st_i64(cpu_tmp1_i64, cpu_env, d_offset);
}
