Rollup merge of #97838 - durin42:llvm-15-hexagon, r=Amanieu

hexagon: adapt test for upstream output changes

The output of IR formatting changed slightly in upstream rev
a0bc67e555f404d0e7ddb2e78cb891d96eaf913d
(https://reviews.llvm.org/D123096). I'm not actually sure what any of
that means, as I don't even know what hexagon is in this context, but
this change allows the test to pass on both old and new LLVMs.

r? ``@nikic``