title: Primeng p-selectButton doesn't work with Reactive Forms
body: <p>I'm using a reactive form with I have a p-selectButton with a formControlName "role".</p>
  
  <p>What I want to do is, put active p-selectButton option with my the received data from my user, but this doesn't work. I don't found a solution in the documentation because only shows how to use it with [(ngModel)]...</p>
  
  <p>this is my code:</p>
  
  <p>ts</p>
  
  <pre><code>this.form = new FormGroup({
          role: new FormControl(null, Validators.required)
  });
  </code></pre>
  
  <p>html</p>
  
  <pre><code>&lt;p-selectButton [options]="roles" formControlName="role" optionLabel="name" multiple="multiple"&gt;&lt;/p-selectButton&gt;
  </code></pre>
  
  <p>All my p-selectButtons options, "roles":</p>
  
  <pre><code>[
    0:
      _id: "5e00a7240742771f183a9f55"
      name: "ADMIN"
      role: "ADMIN_ROLE"
    1:
      _id: "5e00bf010930fa2b5c7d92a1"
      name: "Ventas"
      role: "USER_ROLE"
    ]
  </code></pre>
  
  <p>The p-selectedButton I want to active from my user:</p>
  
  <pre><code>user: {
      role: [
         0: {
           _id: "5e00a7240742771f183a9f55"
           name: "ADMIN"
           role: "ADMIN_ROLE"
         }
      ]
   }
  </code></pre>
  
  <p>And this is how I introduce the selected data in my form (I don't know, Is this the best way? :D)</p>
  
  <pre><code>this.form.get('role').setValue(user.role);
  </code></pre>
  
  <p>If I show in console the form.value.role I can see the expected value, but in the frontend doesn't show the active p-selectButton!!! I have left something?????</p>
  
  <p>Thanks in advance!</p>