[llvm] [X86][GISel] Use Register and MCRegister. NFC (PR #130907)

[Evgenii Kudriashov via llvm-commits]

================
@@ -218,14 +218,14 @@ struct X86IncomingValueHandler : public CallLowering::IncomingValueHandler {
 
   void assignValueToReg(Register ValVReg, Register PhysReg,
                         const CCValAssign &VA) override {
-    markPhysRegUsed(PhysReg);
+    markPhysRegUsed(PhysReg.asMCReg());
----------------
e-kud wrote:

Just finished checking, no unexpected failures on benchmarks.

https://github.com/llvm/llvm-project/pull/130907