dcbnl: Add support for setapp/getapp commands to dcbnl

dcbnl: Add support for setapp/getapp commands to dcbnl

This patch adds dcbnl command definitions to support setapp/getapp
functionality from the IEEE 802.1Qaz Data Center Bridging Capability
Exchange protocol (DCBX) specification. Section 3.3 defines the
application protocol and its 802.1p user priority in DCBX, which is
implemented here as a pair of setapp/getapp commands in the kernel
dcbnl for setting and retrieving the user priority for an given
application protocol. The protocol is identified by the combination of
an id and an idtype. Currently, when idtype is 0, the corresponding
id gives the ether type of this protocol, e.g., for FCoE, it will be
0x8906; when idtype is 1, then the corresponding id gives the TCP or
UDP port number.

For more information regarding DCBX spec., please refer to the following:
http://www.ieee802.org/1/files/public/docs2008/
az-wadekar-dcbx-capability-exchange-discovery-protocol-1108-v1.01.pdf

Signed-off-by: Yi Zou <yi.zou@intel.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>