sh_eth: add sh_eth_cpu_data::no_tx_cntrs flag

RZ/A1H (R7S72100) Ether controller doesn't  seem to have the TX counter
registers like TROCR/CDCR/LCCR (or at least they are still undocumented
like some TSU registers), so we bail out of sh_eth_get_stats() early in
this case.  Currently we are calling sh_eth_is_rz_fast_ether() in order
to check for this, but it would be simpler to check the new 'no_tx_cntrs'
bitfield in the 'struct sh_eth_cpu_data'; then we'd be able  to remove
sh_eth_is_rz_fast_ether() as there would be no callers left...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/sh_eth.c

@@ -455,11 +455,6 @@ static bool sh_eth_is_gether(struct sh_eth_private *mdp)
 	return mdp->reg_offset == sh_eth_offset_gigabit;
 }
 
-static bool sh_eth_is_rz_fast_ether(struct sh_eth_private *mdp)
-{
-	return mdp->reg_offset == sh_eth_offset_fast_rz;
-}
-
 static void sh_eth_select_mii(struct net_device *ndev)
 {
 	struct sh_eth_private *mdp = netdev_priv(ndev);
@@ -614,6 +609,7 @@ static struct sh_eth_cpu_data r7s72100_data = {
 	.xdfar_rw	= 1,
 	.hw_checksum	= 1,
 	.tsu		= 1,
+	.no_tx_cntrs	= 1,
 };
 
 static void sh_eth_chip_reset_r8a7740(struct net_device *ndev)
@@ -2534,7 +2530,7 @@ static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev)
 {
 	struct sh_eth_private *mdp = netdev_priv(ndev);
 
-	if (sh_eth_is_rz_fast_ether(mdp))
+	if (mdp->cd->no_tx_cntrs)
 		return &ndev->stats;
 
 	if (!mdp->is_opened)

drivers/net/ethernet/renesas/sh_eth.h

@@ -514,6 +514,7 @@ struct sh_eth_cpu_data {
 	unsigned rmiimode:1;	/* EtherC has RMIIMODE register */
 	unsigned rtrate:1;	/* EtherC has RTRATE register */
 	unsigned magic:1;	/* EtherC has ECMR.MPDE and ECSR.MPD */
+	unsigned no_tx_cntrs:1;	/* EtherC DOES NOT have TX error counters */
 	unsigned dual_port:1;	/* Dual EtherC/E-DMAC */
 };