[llvm] [SystemZ][z/OS] Remove use of subsections. (PR #184167)

[Tony Tao via llvm-commits]

tltao wrote:

According to the [docs](https://www.ibm.com/docs/en/zos/2.5.0?topic=environment-prolog-information-blocks): `Program Prolog Area-1 (PPA1) appears for every Language Environment® entry point. There is a one-to-one correlation between a PPA1 and a DSA.`

Is it okay to move the location from after every function to the end of the file?

https://github.com/llvm/llvm-project/pull/184167