[llvm] [ARM][Thumb1] Consider tBfar safe in noreturn functions (PR #193240)

[Simon Tatham via llvm-commits]

statham-arm wrote:

Abandoning this PR. It turned out to be harder than I'd thought because of the risk of things other than a return instruction needing LR, and in any case, #203318 has solved the problem this was intended to address.

(It might in principle still be a good idea to do this, but not important.)

https://github.com/llvm/llvm-project/pull/193240