[llvm] [SystemZ] Remove getInliningThresholdMultiplier() override (PR #94612)

[Nikita Popov via llvm-commits]

nikic wrote:

I've update this PR to change the threshold multiplier from 3 to 2 (instead of 1). Based on the numbers in https://github.com/llvm/llvm-project/pull/94612#issuecomment-2244879367, at the multiplier of 2 only imagick has significant negative performance impact, and the s390x backend is currently over-specialized towards that benchmark. The original proposal to use multiplier 1 had negative impact on more benchmarks.

https://github.com/llvm/llvm-project/pull/94612