GVSP: Missing break in switch (CID 1247683 & 1247684)

Change-Id: Ibd3aef4101126f02453bab10cd5ca31e716334de
Reviewed-on: https://code.wireshark.org/review/5617
Reviewed-by: W Moxam <warrenm@ptgrey.com>
Reviewed-by: Anders Broman <a.broman58@gmail.com>