sfc: support second + quarter ns time format for receive datapath
The time_format that we stash in the PTP data structure is never
referenced, so we can remove it. Instead, store the information needed
to interpret sync event timestamps.
Also rolls in a couple of other related minor PTP fixes.
Based on patches by Bert Kenward <bkenward@solarflare.com> and Laurence
Evans <levans@solarflare.com>.
Signed-off-by: Edward Cree <ecree@solarflare.com> Signed-off-by: David S. Miller <davem@davemloft.net>