config: make AVX and AVX512 configurable

config: make AVX and AVX512 configurable

Making AVX and AVX512 configurable is useful for performance and power
testing.

The similar kernel patch at https://patchwork.kernel.org/patch/9618883/.

AVX512 support like in rte_memcpy has been in DPDK since 16.04, but it's
still unproven in rich use cases in hardware. Therefore it's marked as
experimental for now, will enable it after enough field test and possible
optimization.

Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Reviewed-by: Zhiyong Yang <zhiyong.yang@intel.com>
Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>