cxgb4: use unaligned conversion for fetching timestamp

Use get_unaligned_be64() to fetch the timestamp needed for ns_to_ktime()
conversion.

Fixes following sparse warning:
sge.c:3282:43: warning: cast to restricted __be64

Fixes: a4569504 ("cxgb4: time stamping interface for PTP")
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/sge.c

@@ -3312,7 +3312,7 @@ static noinline int t4_systim_to_hwstamp(struct adapter *adapter,
 
 	hwtstamps = skb_hwtstamps(skb);
 	memset(hwtstamps, 0, sizeof(*hwtstamps));
-	hwtstamps->hwtstamp = ns_to_ktime(be64_to_cpu(*((u64 *)data)));
+	hwtstamps->hwtstamp = ns_to_ktime(get_unaligned_be64(data));
 
 	return RX_PTP_PKT_SUC;
 }