[ADT] Remove DenseMapBase::getHashValue (NFC) (#161123)

This patch removes:

  static unsigned getHashValue(const KeyT &Val) {
    return KeyInfoT::getHashValue(Val);
  }

This function is redundant given the templated overload:

  template <typename LookupKeyT>
  static unsigned getHashValue(const LookupKeyT &Val) {
    return KeyInfoT::getHashValue(Val);
  }

Note that the callers doFind and LookupBucketFor are themselves
templated on LookupKeyT.

Author: kazutakahirata

llvm/include/llvm/ADT/DenseMap.h

@@ -440,10 +440,6 @@ class DenseMapBase : public DebugEpochBase {
     }
   }
 
-  static unsigned getHashValue(const KeyT &Val) {
-    return KeyInfoT::getHashValue(Val);
-  }
-
   template <typename LookupKeyT>
   static unsigned getHashValue(const LookupKeyT &Val) {
     return KeyInfoT::getHashValue(Val);