node: choose vector path at runtime

node: choose vector path at runtime

When choosing the vector path, max SIMD bitwidth is now checked to
ensure the vector path is suitable. To do this, the scalar function is
chosen by default in the struct, but at node initialisation time, this
function pointer is updated to the vector version if supported, and
if it is within the max SIMD bitwidth limit.

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Nithin Dabilpuram <ndabilpuram@marvell.com>