bnxt_en: Add 57500 new chip ID and basic structures.

57500 series is a new chip class (P5) that requires some driver changes
in the next several patches.  This adds basic chip ID, doorbells, and
the notification queue (NQ) structures.  Each MSIX is associated with an
NQ instead of a CP ring in legacy chips.  Each NQ has up to 2 associated
CP rings for RX and TX.  The same bnxt_cp_ring_info struct will be used
for the NQ.

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