bnxt_en: Support for Short Firmware Message

The new short message format is used on the new BCM57454 VFs.  Each
firmware message is a fixed 16-byte message sent using the standard
firmware communication channel.  The short message has a DMA address
pointing to the legacy long firmware message.

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