[NFC][llvm] Inclusive language: remove instance of master in LiveRangeUtils.h

[quinnp]

Summary

[NFC] As part of using inclusive language within the llvm project, this patch
replaces master with primary in LiveRangeUtils.h.

[MatzeB]

Sure

llvm/lib/CodeGen/LiveRangeUtils.h

 #ifndef LLVM_LIB_CODEGEN_LIVERANGEUTILS_H
 #define LLVM_LIB_CODEGEN_LIVERANGEUTILS_H
 
 #include "llvm/CodeGen/LiveInterval.h"
 
 namespace llvm {
 
 /// Helper function that distributes live range value numbers and the
-/// corresponding segments of a master live range \p LR to a list of newly
+/// corresponding segments of a primary live range \p LR to a list of newly
 /// created live ranges \p SplitLRs. \p VNIClasses maps each value number in \p
 /// LR to 0 meaning it should stay or to 1..N meaning it should go to a specific
 /// live range in the \p SplitLRs array.
 template<typename LiveRangeT, typename EqClassesT>
 static void DistributeRange(LiveRangeT &LR, LiveRangeT *SplitLRs[],
                             EqClassesT VNIClasses) {
   // Move segments to new intervals.
   typename LiveRangeT::iterator J = LR.begin(), E = LR.end();