Add ARM test for r227489, but XFAIL because this is actually more work than it appear...

Also revert r227489 since it didn't actually fix the thing I thought I
was fixing (since the test case was targeting the wrong architecture
initially). The change might be correct & demonstrated by other test
cases, but it's not a priority for me to find those test cases right
now.

Filed PR22417 for the failure.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227632 91177308-0d34-0410-b5e6-96231b3b80d8