bnxt_en: Implement DCBNL to support host-based DCBX.

bnxt_en: Implement DCBNL to support host-based DCBX.

Orabug: 24567991

Support only IEEE DCBX initially.  Add IEEE DCBNL ops and functions to
get and set the hardware DCBX parameters.  The DCB code is conditional on
Kconfig CONFIG_BNXT_DCB.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 7df4ae9fe85567a1710048da8229bd85e0da9df7)
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
	drivers/net/ethernet/broadcom/bnxt/bnxt.c

Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>