net: dsa: mv888e6xxx: do not use netdev printing

The mv888e6xxx driver accesses a port's netdev mostly for printing.

This is bad for 2 reasons: DSA and CPU ports do not have a netdev
pointer; it doesn't give us a correct picture of why a DSA driver might
need to access a port's netdev.

Instead simply use dev_* printing functions with chip->dev (or ds->dev
depending on the scope, both guaranteed to exist), with a p%d prefix for
the target port.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>