[Metadata] Make range boundary variables unsigned (NFC)

They should be unsigned because the source and target value are too.

llvm/lib/IR/Metadata.cpp

@@ -1287,12 +1287,12 @@ MDNode *MDNode::getMostGenericRange(MDNode *A, MDNode *B) {
     return A;
 
   // First, walk both lists in order of the lower boundary of each interval.
-  // At each step, try to merge the new interval to the last one we adedd.
+  // At each step, try to merge the new interval to the last one we added.
   SmallVector<ConstantInt *, 4> EndPoints;
-  int AI = 0;
-  int BI = 0;
-  int AN = A->getNumOperands() / 2;
-  int BN = B->getNumOperands() / 2;
+  unsigned AI = 0;
+  unsigned BI = 0;
+  unsigned AN = A->getNumOperands() / 2;
+  unsigned BN = B->getNumOperands() / 2;
   while (AI < AN && BI < BN) {
     ConstantInt *ALow = mdconst::extract<ConstantInt>(A->getOperand(2 * AI));
     ConstantInt *BLow = mdconst::extract<ConstantInt>(B->getOperand(2 * BI));