Since dev->dsa_ptr is a pointer to a dsa_switch_tree, there is no need
to have another inline helper just to check rcv.

Remove dsa_uses_tagged_protocol and check dsa_ptr && dsa_ptr->rcv
together at the same time.
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>