[InstCombine] Use getFreedOperand() (NFC)

Use getFreedOperand() instead of isFreeCall() to remove the
implicit assumption that any pointer operand to a free function
is the operand being freed. This won't actually matter until we
handle allockind(free).

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -2801,7 +2801,8 @@ static bool isAllocSiteRemovable(Instruction *AI,
           continue;
         }
 
-        if (isFreeCall(I, &TLI) && getAllocationFamily(I, &TLI) == Family) {
+        if (getFreedOperand(cast<CallBase>(I), &TLI) == PI &&
+            getAllocationFamily(I, &TLI) == Family) {
           assert(Family);
           Users.emplace_back(I);
           continue;