Add multithreading support to the x86_64 zdot kernel (#2222)
Add multithreading support to the x86_64 zdot kernel (#2222)

* Add multithreading support

copied from the ThunderX2T99 kernel. For #2221

xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS,xianyi/OpenBLAS