[llvm] [MachineLICM] Use `RegisterClassInfo::getRegPressureSetLimit` (PR #211715)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

> Looks like a bunch of tests are failing after this and have been for a few hours. What's the plan? Is a fix about to land, or should we revert?

It is because of failure in experimental M68k target, which was not found during precommit CI testing. I don't know if we should care about it. I will revert it first.

https://github.com/llvm/llvm-project/pull/211715