Extend reg_is_simd to consider ZMM registers as well.

Current implementation of reg_is_simd does not consider ZMM as simd.

bool
reg_is_simd(reg_id_t reg)
{
    return reg_is_xmm(reg) /*includes ymm*/ || reg_is_mmx(reg);
}

Issue relates to extending reg_is_simd to checking ZMM registers as well.