This just tweaks the fix for D145232 to make the limit more precise, so
that we could actually emit a delay of 3 SALU cycles (the maximum) if we
had any SALU instructions that required it.
Not sure why this was broken, but I was seeing this linker error:
ld64.lld: error: undefined symbol: (anonymous namespace)::AMDGPUInsertDelayAlu::DelayInfo::SALU_CYCLES_MAX
>>> referenced by AMDGPUInsertDelayAlu.cpp:129 (/Users/matt/src/llvm-project/llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp:129)