Add another check-label to test to avoid any bad checks

Author: jack-slingsby

mlir/test/Dialect/Index/inliner-interface.mlir

@@ -8,6 +8,7 @@ func.func @main(%arg0: i32) -> index {
   return %0 : index
 }
 
+// CHECK-LABEL: @f
 func.func @f(%arg0: i32) -> index {
   %0 = index.castu %arg0 : i32 to index
   return %0 : index