SDNode already had ops() which would iterate over the operands and return
SDUse*. This version instead gets the SDValue's out of the SDUse's so that
we can use foreach in more places.
Reviewed by David Blaikie.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240805 91177308-0d34-0410-b5e6-96231b3b80d8