added no-conditional-assignment rule and changed files to follow new rule

public/app/features/dashboard/upload.ts

@@ -36,10 +36,13 @@ function uploadDashboardDirective(timer, alertSrv, $location) {
           };
         };
 
-        for (let i = 0, f; (f = files[i]); i++) {
+        let i = 0;
+        let f = files[i];
+        for (i; f; i++) {
           const reader = new FileReader();
           reader.onload = readerOnload();
           reader.readAsText(f);
+          f = files[i];
         }
       }