sfc: only advertise TX timestamping if we have the license for it

sfc: only advertise TX timestamping if we have the license for it

BugLink: https://bugs.launchpad.net/bugs/1836635
We check the license for TX hardware timestamping capability.
The PTP probe will have enabled PTP sync events from the adapter.  If
 later, at TX queue init, it turns out we do not have the license, we
 don't need the sync events either.

Signed-off-by: Martin Habets <mhabets@solarflare.com>
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 6aa47c87cb053670bb636fb2001deb4a868f9486)
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>