[llvm] [CodeGen] Get rid of incorrect `std` template specializations (PR #160804)

[A. Jiang via llvm-commits]

================
@@ -334,42 +361,17 @@ template <> struct hash<llvm::rdf::RegisterAggr> {
   }
 };
 
-template <> struct equal_to<llvm::rdf::RegisterRef> {
-  constexpr equal_to(const llvm::rdf::PhysicalRegisterInfo &pri) : PRI(&pri) {}
-
-  bool operator()(llvm::rdf::RegisterRef A, llvm::rdf::RegisterRef B) const {
-    return PRI->equal_to(A, B);
-  }
-
-private:
-  // Make it a pointer just in case. See comment in `less` below.
-  const llvm::rdf::PhysicalRegisterInfo *PRI;
-};
-
 template <> struct equal_to<llvm::rdf::RegisterAggr> {
   bool operator()(const llvm::rdf::RegisterAggr &A,
                   const llvm::rdf::RegisterAggr &B) const {
     return A == B;
   }
 };
----------------
frederick-vs-ja wrote:

This full specialization is correct but probably meaningless. Perhaps we should remove it in a later PR.

https://github.com/llvm/llvm-project/pull/160804