[turbofan] Fix several int vs size_t issues.

src/compiler/x64/instruction-selector-x64.cc

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index 9c1985961a2a82d91a28f05549b9176d108c9aca..48c6d80664b546842d31ff0340c4b855c015ed29 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -346,8 +346,8 @@ static void VisitBinop(InstructionSelector* selector, Node* node,
     outputs[output_count++] = g.DefineAsRegister(cont->result());
   }
 
-  DCHECK_NE(0, static_cast<int>(input_count));
-  DCHECK_NE(0, static_cast<int>(output_count));
+  DCHECK_NE(0u, input_count);
+  DCHECK_NE(0u, output_count);
   DCHECK_GE(arraysize(inputs), input_count);
   DCHECK_GE(arraysize(outputs), output_count);
 
@@ -471,7 +471,7 @@ void EmitLea(InstructionSelector* selector, InstructionCode opcode,
   AddressingMode mode = g.GenerateMemoryOperandInputs(
       index, scale, base, displacement, inputs, &input_count);
 
-  DCHECK_NE(0, static_cast<int>(input_count));
+  DCHECK_NE(0u, input_count);
   DCHECK_GE(arraysize(inputs), input_count);
 
   InstructionOperand outputs[1];