net: dsa: b53: Add support for BCM585xx/586xx/88312 integrated switch

Update the SRAB, core driver and binding document to support the
BCM585xx/586xx/88312 integrated switch (Northstar Plus SoCs family).

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/b53/b53_priv.h

@@ -59,6 +59,7 @@ enum {
 	BCM53012_DEVICE_ID = 0x53012,
 	BCM53018_DEVICE_ID = 0x53018,
 	BCM53019_DEVICE_ID = 0x53019,
+	BCM58XX_DEVICE_ID = 0x5800,
 };
 
 #define B53_N_PORTS	9