[InstSimplify] add tests for funnel shift with undef operands; NFC

These are part of D54666, so adding them here before the patch to
show the baseline (currently unoptimized) results.

Patch by: @nikic (Nikita Popov)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@347331 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed