Set about phone subtext to device model string.

Also remove useless custom preference

Fix: 36395109
Test: robotests
Change-Id: I07297e6ade6991a8262473c9f59c21d914300244

src/com/android/settings/deviceinfo/DeviceModelPreferenceController.java

@@ -46,7 +46,7 @@ public class DeviceModelPreferenceController extends PreferenceController {
         super.displayPreference(screen);
         final Preference pref = screen.findPreference(KEY_DEVICE_MODEL);
         if (pref != null) {
-            pref.setSummary(Build.MODEL + DeviceInfoUtils.getMsvSuffix());
+            pref.setSummary(getDeviceModel());
         }
     }
 
@@ -64,4 +64,8 @@ public class DeviceModelPreferenceController extends PreferenceController {
         fragment.show(mHost.getFragmentManager(), HardwareInfoDialogFragment.TAG);
         return true;
     }
+
+    public static String getDeviceModel() {
+        return Build.MODEL + DeviceInfoUtils.getMsvSuffix();
+    }
 }