bnxt_en: Add BCM58700 PCI device ID for NS2 Nitro.

A bridge device in NS2 has the same device ID as the ethernet controller.
Add check to avoid probing the bridge device.

Signed-off-by: Prashant Sreedharan <prashant.sreedharan@broadcom.com>
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>