[mlir][linalg][nfc] Fix signed/unsigned comparison warning in header

[bondhugula]

mlir/include/mlir/Dialect/Linalg/IR/LinalgOps.td

698–711

Side note: This much C++ code shouldn't have been put in a .td file. It's hard for a developer to also notice such errors via in-editor syntax checkers, code completion engines, etc. This op is full of long C++ code. git blame shows @pifon2a for all these lines. Do we have a policy here? @rriddle @mehdi_amini

mlir/include/mlir/Dialect/Linalg/IR/LinalgOps.td

OpOperand& appendOutputOperand(OpBuilder& builder, Value operand) {
           TiledLoopOp::getOperandSegmentSizeAttr(),
           builder.getI32VectorAttr(
               {numLoops, numLoops, numLoops, numInputs, numOutputs + 1}));
       return getOperation()->getOpOperand(getNumControlOperands() + numInputs +
                                           numOutputs);
     }
 
     /// Erase `operand` from the `input` or `output` arguments.
     void eraseOperand(OpBuilder& builder, OpOperand& operand) {
       int numInputs = getNumInputs();
       int numLoops = getNumLoops();
       int numOutputs = getNumOutputs();
       int numControlOperands = getNumControlOperands();
 
-      auto operandIndex = operand.getOperandNumber();
+      int operandIndex = operand.getOperandNumber();
       assert(operandIndex >= numControlOperands &&
-             operandIndex < getNumOperands() &&
+             operandIndex < static_cast<int>(getNumOperands()) &&
              "Can erase only `input` or `output` operand");
 
       if (operandIndex >= numControlOperands + numInputs)
         --numOutputs;
       else
         --numInputs;
 
       getOperation()->eraseOperand(operandIndex);
       getBody()->eraseArgument(operandIndex - 2 * numLoops);
       getOperation()->setAttr(
           TiledLoopOp::getOperandSegmentSizeAttr(),
           builder.getI32VectorAttr(
               {numLoops, numLoops, numLoops, numInputs, numOutputs}));