staging: rtl8723au: issue_probersp(): Don't insert beacon data twice

In case of AP mode, we were inserting the beacon data twice in the
probe_resp frame, leading to a corrupted on the wire frame.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>