Revert "net: gptp: Fix announce message len"

This reverts commit 6b644dff.

Reason: breaks Peer-to-Peer gPTP connection. A better solution should be
found to handle the optional TLV on the announce message (chapter 10.5.1
IEEE 802.1AS-2011)

Signed-off-by: Mario Paja <mario.paja@zal.aero>