[SPIRV] Use MCRegister instead of unsigned. NFC (#167585)

Author: topperc

llvm/lib/Target/SPIRV/MCTargetDesc/SPIRVInstPrinter.h

@@ -16,11 +16,12 @@
 #include "MCTargetDesc/SPIRVBaseInfo.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/MC/MCInstPrinter.h"
+#include "llvm/MC/MCRegister.h"
 
 namespace llvm {
 class SPIRVInstPrinter : public MCInstPrinter {
 private:
-  SmallDenseMap<unsigned, SPIRV::InstructionSet::InstructionSet> ExtInstSetIDs;
+  SmallDenseMap<MCRegister, SPIRV::InstructionSet::InstructionSet> ExtInstSetIDs;
   void recordOpExtInstImport(const MCInst *MI);
 
 public: