net: dsa: mv88e6xxx: Factor out common initialization code

Code used and needed in mv886xxx.c should be initialized there as well,
so factor it out from the individual initialization files.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dsa/mv88e6xxx.h b/drivers/net/dsa/mv88e6xxx.h
index 5fd42ce..a02d95a 100644
--- a/drivers/net/dsa/mv88e6xxx.h
+++ b/drivers/net/dsa/mv88e6xxx.h
@@ -57,6 +57,7 @@
 	int reg;
 };
 
+int mv88e6xxx_setup_common(struct dsa_switch *ds);
 int __mv88e6xxx_reg_read(struct mii_bus *bus, int sw_addr, int addr, int reg);
 int mv88e6xxx_reg_read(struct dsa_switch *ds, int addr, int reg);
 int __mv88e6xxx_reg_write(struct mii_bus *bus, int sw_addr, int addr,