net: dsa: mv88e6xxx: move ATU ageing time setter

Move the ATU ageing time setter code in a new global1_atu.c file, which
will be extended in future patches to contains all consequent Global (1)
ATU support code.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/global1.h

@@ -38,4 +38,7 @@ int mv88e6095_g1_set_cpu_port(struct mv88e6xxx_chip *chip, int port);
 int mv88e6390_g1_set_cpu_port(struct mv88e6xxx_chip *chip, int port);
 int mv88e6390_g1_mgmt_rsvd2cpu(struct mv88e6xxx_chip *chip);
 
+int mv88e6xxx_g1_atu_set_age_time(struct mv88e6xxx_chip *chip,
+				  unsigned int msecs);
+
 #endif /* _MV88E6XXX_GLOBAL1_H */