net: dsa: remove dsa_port_is_bridged

The helper is only used once and makes the code more complicated that it
should. Remove it and reorganize the variables so that it fits on 80
columns.

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