[Hexagon] Adding multiply with rnd/sat/rndsat

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224265 91177308-0d34-0410-b5e6-96231b3b80d8
[Hexagon] Adding accumulating half word multiplies.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224266 91177308-0d34-0410-b5e6-96231b3b80d8
[Hexagon] Adding doubleworld accumulating multiplies of halfwords.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224267 91177308-0d34-0410-b5e6-96231b3b80d8