[MachineSink] Use RegisterClassInfo::getRegPressureSetLimit (#119830)

`RegisterClassInfo::getRegPressureSetLimit` is a wrapper of
`TargetRegisterInfo::getRegPressureSetLimit` with some logics to
adjust the limit by removing reserved registers.

It seems that we shouldn't use
`TargetRegisterInfo::getRegPressureSetLimit`
directly, just like the comment "This limit must be adjusted
dynamically for reserved registers" said.

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

llvm/lib/CodeGen/MachineSink.cpp

@@ -1098,7 +1098,7 @@ bool MachineSinking::registerPressureSetExceedsLimit(
   std::vector<unsigned> BBRegisterPressure = getBBRegisterPressure(MBB);
   for (; *PS != -1; PS++)
     if (Weight + BBRegisterPressure[*PS] >=
-        TRI->getRegPressureSetLimit(*MBB.getParent(), *PS))
+        RegClassInfo.getRegPressureSetLimit(*PS))
       return true;
   return false;
 }