move scalar code which does not use x86 intrinsic functions to new file
"i40e_rxtx_vec_common.h", while keeping x86 code in i40e_rxtx_vec.c.
This allows the scalar code to to be shared among vector drivers for
different platforms.
Signed-off-by: Jianbo Liu <jianbo.liu@linaro.org>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
