bnxt_en: Add support for 2nd firmware message channel.

Earlier, some of the firmware commands (ex: CFA_FLOW_*) which are processed
by KONG processor were sent to the CHIMP processor from the host. This
approach was taken as there was no direct message channel to KONG.
CHIMP in turn used to send them to KONG. Newer firmware supports a new
message channel which the host can send messages directly to the KONG
processor.

This patch adds support for required changes needed in the driver
to support direct KONG message channel.  This speeds up flow related
messages sent to the firmware for CLS_FLOWER offload.

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