UpdateTestChecks: hexagon support

Summary:
These tests are being affected by an upcoming patch,
so having an understandable (autogenerated) diff is helpful.

This target, again, prefers `-march`:
```
llvm/test/CodeGen/Hexagon$ grep -r triple | wc -l
467
llvm/test/CodeGen/Hexagon$ grep -r march | wc -l
1167
```

Reviewers: RKSimon, kparzysz

Reviewed By: kparzysz

Subscribers: xbolva00, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62867

llvm-svn: 362605