[llvm] [MCSchedule][NFC] Use constexpr for static constants (PR #209934)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ml-opt-dev-x86-64` running on `ml-opt-dev-x86-64-b1` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/137/builds/43109

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/Mips/msa/f16-llvm-ir.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/b/ml-opt-dev-x86-64-b1/build/bin/llc -relocation-model=pic -mtriple=mipsel-- -mcpu=mips32r5 -mattr=+abs2008      -mattr=+fp64,+msa -verify-machineinstrs -mips-jalr-reloc=false < /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll | /b/ml-opt-dev-x86-64-b1/build/bin/FileCheck /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll      --check-prefixes=MIPS32,MIPS32-O32
# executed command: /b/ml-opt-dev-x86-64-b1/build/bin/llc -relocation-model=pic -mtriple=mipsel-- -mcpu=mips32r5 -mattr=+abs2008 -mattr=+fp64,+msa -verify-machineinstrs -mips-jalr-reloc=false
# executed command: /b/ml-opt-dev-x86-64-b1/build/bin/FileCheck /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll --check-prefixes=MIPS32,MIPS32-O32
# .---command stderr------------
# | /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll:1100:16: error: MIPS32-NEXT: is not on the line after the previous match
# | ; MIPS32-NEXT: jalr $25
# |                ^
# | <stdin>:576:2: note: 'next' match was here
# |  jalr $25
# |  ^
# | <stdin>:574:28: note: previous match ended here
# |  lw $25, %call16(powf)($gp)
# |                            ^
# | <stdin>:575:1: note: non-matching line after previous match is here
# |  # kill: def $f12 killed $f12 killed $w12
# | ^
# | /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll:1203:16: error: MIPS32-NEXT: is not on the line after the previous match
# | ; MIPS32-NEXT: jalr $25
# |                ^
# | <stdin>:624:2: note: 'next' match was here
# |  jalr $25
# |  ^
# | <stdin>:622:29: note: previous match ended here
# |  lw $25, %call16(log2f)($gp)
# |                             ^
# | <stdin>:623:1: note: non-matching line after previous match is here
# |  # kill: def $f12 killed $f12 killed $w12
# | ^
# | /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll:1303:16: error: MIPS32-NEXT: is not on the line after the previous match
# | ; MIPS32-NEXT: jalr $25
# |                ^
# | <stdin>:672:2: note: 'next' match was here
# |  jalr $25
# |  ^
# | <stdin>:670:30: note: previous match ended here
# |  lw $25, %call16(log10f)($gp)
# |                              ^
# | <stdin>:671:1: note: non-matching line after previous match is here
# |  # kill: def $f12 killed $f12 killed $w12
# | ^
# | /b/ml-opt-dev-x86-64-b1/llvm-project/llvm/test/CodeGen/Mips/msa/f16-llvm-ir.ll:1464:16: error: MIPS32-NEXT: is not on the line after the previous match
# | ; MIPS32-NEXT: jalr $25
# |                ^
# | <stdin>:756:2: note: 'next' match was here
...

```

</details>

https://github.com/llvm/llvm-project/pull/209934