[llvm] [X86] Recognize POP/ADD/SUB modifying rsp in getSPAdjust. (PR #114265)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon approved this pull request.

LGTM - but please be vigilant as I wonder if other obscure instructions may be used as well and could fire that assert in an external test case.

https://github.com/llvm/llvm-project/pull/114265