net: sfc: remove redundant variable start

Variable start is assigned but never read hence it is redundant
and can be removed. Cleans up clang warning:

drivers/net/ethernet/sfc/ptp.c:655:2: warning: Value stored to 'start'
is never read
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NBert Kenward <bkenward@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ptp.c

@@ -648,11 +648,9 @@ static void efx_ptp_send_times(struct efx_nic *efx,
 	struct pps_event_time now;
 	struct timespec64 limit;
 	struct efx_ptp_data *ptp = efx->ptp_data;
-	struct timespec64 start;
 	int *mc_running = ptp->start.addr;
 
 	pps_get_ts(&now);
-	start = now.ts_real;
 	limit = now.ts_real;
 	timespec64_add_ns(&limit, SYNCHRONISE_PERIOD_NS);