net: Remove usage of net_device last_rx member

The network stack no longer uses the last_rx member of struct net_device
since the bonding driver switched to use its own private last_rx in
commit 9f242738376d ("bonding: use last_arp_rx in slave_last_rx()").

However, some drivers still (ab)use the field for their own purposes and
some driver just update it without actually using it.

Previously, there was an accompanying comment for the last_rx member
added in commit 4dc89133f49b ("net: add a comment on netdev->last_rx")
which asked drivers not to update is, unless really needed. However,
this commend was removed in commit f8ff080dacec ("bonding: remove
useless updating of slave->dev->last_rx"), so some drivers added later
on still did update last_rx.

Remove all usage of last_rx and switch three drivers (sky2, atp and
smc91c92_cs) which actually read and write it to use their own private
copy in netdev_priv.

Compile-tested with allyesconfig and allmodconfig on x86 and arm.

Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: Mirko Lindner <mlindner@marvell.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
index be003c5..2b2cc3f 100644
--- a/drivers/net/ethernet/marvell/sky2.c
+++ b/drivers/net/ethernet/marvell/sky2.c
@@ -2666,7 +2666,7 @@ static inline void sky2_rx_done(struct sky2_hw *hw, unsigned port,
 	sky2->rx_stats.bytes += bytes;
 	u64_stats_update_end(&sky2->rx_stats.syncp);
 
-	dev->last_rx = jiffies;
+	sky2->last_rx = jiffies;
 	sky2_rx_update(netdev_priv(dev), rxqaddr[port]);
 }
 
@@ -2953,7 +2953,7 @@ static int sky2_rx_hung(struct net_device *dev)
 	u8 fifo_lev = sky2_read8(hw, Q_ADDR(rxq, Q_RL));
 
 	/* If idle and MAC or PCI is stuck */
-	if (sky2->check.last == dev->last_rx &&
+	if (sky2->check.last == sky2->last_rx &&
 	    ((mac_rp == sky2->check.mac_rp &&
 	      mac_lev != 0 && mac_lev >= sky2->check.mac_lev) ||
 	     /* Check if the PCI RX hang */
@@ -2965,7 +2965,7 @@ static int sky2_rx_hung(struct net_device *dev)
 			      fifo_rp, sky2_read8(hw, Q_ADDR(rxq, Q_WP)));
 		return 1;
 	} else {
-		sky2->check.last = dev->last_rx;
+		sky2->check.last = sky2->last_rx;
 		sky2->check.mac_rp = mac_rp;
 		sky2->check.mac_lev = mac_lev;
 		sky2->check.fifo_rp = fifo_rp;