Revert "Move function to obtain branch weights into the BranchInst class. NFC."

This reverts commit r223784 and copies the 'ExtractBranchMetadata' to CodeGenPrepare.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223795 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Instructions.h

@@ -2535,10 +2535,6 @@ public:
   /// continues to map correctly to each operand.
   void swapSuccessors();
 
-  /// \brief Retrieve the probabilities of a conditional branch. Returns true on
-  /// success, or returns false if no or invalid metadata was found.
-  bool getBranchWeights(uint64_t &TrueWeight, uint64_t &FalseWeight) const;
-
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static inline bool classof(const Instruction *I) {
     return (I->getOpcode() == Instruction::Br);