In commit 5cc194ca,
the number of ehci ports is corrected to six. Fix docs
related to it.

Signed-off-by: npes87184 <npes87184@gmail.com>
Message-id: 20180801122410.10343-1-npes87184@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>