bnxt_en: Check new firmware capability to display extended stats.

Newer firmware now advertises the capability for extended stats
support.  Check the new capability in addition to the existing
version check.

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>