[AArch64] Generate vector signed/unsigned mul and mla/mls long.

Phabricator Revision: http://reviews.llvm.org/D5589
Patch by Balaram Makam <bmakam@codeaurora.org>!!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219276 91177308-0d34-0410-b5e6-96231b3b80d8