Some drivers were calling the skb_tx_timestamp() function only when
a hardware timestamp was not requested. Now that applications can use
the SOF_TIMESTAMPING_OPT_TX_SWHW option to request both software and
hardware timestamps, the drivers need to be modified to unconditionally
call skb_tx_timestamp().

CC: Richard Cochran <richardcochran@gmail.com>
CC: Willem de Bruijn <willemb@google.com>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>