[llvm] [SystemZ] Eliminate call sequence instructions early. (PR #77812)

[Jonas Paulsson via llvm-commits]

JonPsson1 wrote:

Patch updated with a version that gives zero change on SPEC and in tests:
- remove the frame instruction mapping of these pseudos so that they are not recognized and thereby avoid the re-computation of MaxCallFrameSize in PEI.
- Set them all to 0 instead of removing them during isel and instead remove them in processFunctionBeforeFrameFinalized(), during PEI.


https://github.com/llvm/llvm-project/pull/77812