net: dsa: remove gratuitous use of dsa_is_{user,dsa,cpu}_port

Find the occurrences of dsa_is_{user,dsa,cpu}_port where a struct
dsa_port *dp was already available in the function scope, and replace
them with the dsa_port_is_{user,dsa,cpu} equivalent function which uses
that dp directly and does not perform another hidden dsa_to_port().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>