Now that we don't keep live registers across calls, there is not reason to go

Now that we don't keep live registers across calls, there is not reason to go
through the very long list of call-clobbered registers. We just assume all
registers are clobbered.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103930 91177308-0d34-0410-b5e6-96231b3b80d8