bnxt_en: add support for port_attr_get and and get_phys_port_name

This patch adds support for the switchdev_port_attr_get() and
ndo_get_phys_port_name() methods for the PF and the VF-reps.
Using this support a user application can deduce that the PF
(when in the ESWITCH_SWDEV mode) and it's VF-reps form a switch.

Signed-off-by: Sathya Perla <sathya.perla@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>