bnxt_en: fix switchdev port naming for external-port-rep and vf-reps

Fix the phys_port_name for the external physical port to be in
"pA" format and that of VF-rep to be in "pCvfD" format as
suggested by Jakub Kicinski.

Fixes: c124a62f ("bnxt_en: add support for port_attr_get and get_phys_port_name")
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>