bnxt_en: Add basic support for Nitro in North Star 2.

Nitro is the embedded version of the ethernet controller in the North
Star 2 SoC.  Add basic code to recognize the chip ID and disable
the features (ntuple, TPA, ring and port statistics) not supported on
Nitro A0.

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>