bnxt_en: Add additional extended port statistics.

Latest firmware spec. has some additional rx extended port stats and new
tx extended port stats added.  We now need to check the size of the
returned rx and tx extended stats and determine how many counters are
valid.  New counters added include CoS byte and packet counts for rx
and tx.

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