[clang] [Hexagon] Fix B0 macro conflict between hexagon_types.h and termios.h (PR #184539)

[Ankit Aggarwal via cfe-commits]

https://github.com/aankit-ca commented:

I'm fine with this change. Not sure if there's a better fix available for this.
This change will guard the function definition but the call sites for B0 will not work.
Should consider renaming the function too?

https://github.com/llvm/llvm-project/pull/184539