[ARM] Remove XFAIL from passing RT test

This test started passing without warning, so in theory, we shouldn't mark
is as XPASS, but the buildbots are red and there's been an uncaught regression
meanwhile. Since it's passing on {ARM,Thumb2} x {NEON,VFPv3}, I'll risk future
failures for the benefit of getting the bots green again.

llvm-svn: 232642