[llvm] [TRI] Remove reserved registers in getRegPressureSetLimit (PR #118787)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

> Do you know why this doesn't have as many changes to the RISC-V tests as the RISCV-V specific patch?

I did a rough investigation, I think it is because we only changed the limit of `GPRAll` in that RISC-V specific patch, but there are some overlapped register pressure sets like GPRAll, SP, GPRTC, etc. We didn't remove reserved registerd for these register pressure sets.

https://github.com/llvm/llvm-project/pull/118787