vector functions cleanup and improvements

vector functions cleanup and improvements

Remove functions which have native C equivalent (i.e. _is_equal can be
replaced with ==, _add with +)
Add SSE4.2, AVX-512 implementations of splat, load_unaligned, store_unaligned,
is_all_zero, is_equal, is_all_equal

Change-Id: Ie80b0e482e7a76248ad79399c2576468532354cd
Signed-off-by: Damjan Marion <damarion@cisco.com>