net: phy: bcm54140: add cable diagnostics support

Use the generic cable tester functions from bcm-phy-lib to add cable
tester support.

100m cable, A/B/C/D open:
  Cable test started for device eth0.
  Cable test completed for device eth0.
  Pair: Pair A, result: Open Circuit
  Pair: Pair B, result: Open Circuit
  Pair: Pair C, result: Open Circuit
  Pair: Pair D, result: Open Circuit
  Pair: Pair A, fault length: 106.60m
  Pair: Pair B, fault length: 103.32m
  Pair: Pair C, fault length: 104.96m
  Pair: Pair D, fault length: 106.60m

1m cable, A/B connected, pair C shorted, D open:
  Cable test started for device eth0.
  Cable test completed for device eth0.
  Pair: Pair A, result: OK
  Pair: Pair B, result: OK
  Pair: Pair C, result: Short within Pair
  Pair: Pair D, result: Open Circuit
  Pair: Pair C, fault length: 0.82m
  Pair: Pair D, fault length: 1.64m

1m cable, A/B connected, pair C shorted with D:
  Cable test started for device eth0.
  Cable test completed for device eth0.
  Pair: Pair A, result: OK
  Pair: Pair B, result: OK
  Pair: Pair C, result: Short to another pair
  Pair: Pair D, result: Short to another pair
  Pair: Pair C, fault length: 1.64m
  Pair: Pair D, fault length: 1.64m

The granularity of the length measurement seems to be 82cm.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/bcm54140.c

@@ -831,6 +831,7 @@ static struct phy_driver bcm54140_drivers[] = {
 		.phy_id         = PHY_ID_BCM54140,
 		.phy_id_mask    = BCM54140_PHY_ID_MASK,
 		.name           = "Broadcom BCM54140",
+		.flags		= PHY_POLL_CABLE_TEST,
 		.features       = PHY_GBIT_FEATURES,
 		.config_init    = bcm54140_config_init,
 		.did_interrupt	= bcm54140_did_interrupt,
@@ -842,6 +843,8 @@ static struct phy_driver bcm54140_drivers[] = {
 		.soft_reset	= genphy_soft_reset,
 		.get_tunable	= bcm54140_get_tunable,
 		.set_tunable	= bcm54140_set_tunable,
+		.cable_test_start = bcm_phy_cable_test_start_rdb,
+		.cable_test_get_status = bcm_phy_cable_test_get_status_rdb,
 	},
 };
 module_phy_driver(bcm54140_drivers);