net: dsa: mv88e6xxx: specify ageing time limits

Now that DSA has ageing time limits, specify them when registering a
switch so that out-of-range values are handled correctly by the core.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reported-by: Jason Cobham <jcobham@questertangent.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>