[Hexagon] Change .mir testcase to make sure function is not in SSA form

[Hexagon] Change .mir testcase to make sure function is not in SSA form

If a machine function satisfies SSA, the IsSSA property is assumed even
if the pass to be executed runs after existing from SSA. If the pass
output then does not conform to SSA, a verifier error will be flagged
(with expensive checks enabled).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336682 91177308-0d34-0410-b5e6-96231b3b80d8