Add support of Ethernet link bonding utilizing DPDK link bonding

Add support of Ethernet link bonding utilizing DPDK link bonding
poll mode driver library. The bonded interfaces to be created on
VPP startup is specified in the dpdk section of startup.conf
or qn.conf, using DPDK EAL command. Following is an example of a
dpdk section white listing PCI addressses of 4 ethernet interfacess
to be under VPP control plus two bonded interface and the PCI addresses
of the slaves in each:
dpdk { socket-mem 1024,1024
dev 0000:0f:00.0 dev 0000:10:00.0 dev 0000:11:00.0 dev 0000:12:00.0
vdev eth_bond0,mode=2,slave=0000:0f:00.0,slave=0000:11:00.0,xmit_policy=l34
vdev  eth_bond1,mode=2,slave=0000:10:00.0,slave=0000:12:00.0,xmit_policy=l34
}
Note that only balance XOR (mode 2) is supported and "xmit_policy=l34"
specifies to use layer 3 SIP/DIP and layer 4 Sport/Dport for load
balance. Using "xmit_policy=l2" for SMAC/DMAC or "xmit_policy=l23" for
SMAC/DMAC and SIP/DIP should also work.

Change-Id: Iaf6438686fa20cce893cb5a823b76e2886b4360b
Signed-off-by: John Lo <[email protected]>