s4-common: Restrict square preview resolutions from VGA front camera

* The VGA front camera found in fireball and ville appears to be
  incapable of actually using a square preview resolution. Restrict it.
* Addresses failures in certain apps such as Snapchat.
* Resolves INSTALLER-89

Change-Id: I5f65942cdbebc66c3f0d43095e10f3b451bae9b3
pyramid: Set CAMERA_FRONT_VGA flag