bnxt_en: Pass DCB RoCE app priority to firmware.

When the driver gets the RoCE app priority set/delete call through DCBNL,
the driver will send the information to the firmware to set up the
priority VLAN tag for RDMA traffic.

[ New version using the common ETH_P_IBOE constant in if_ether.h ]

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