iproute2 patch to generalize VXLAN forwarding tables

This is the iproute2 support allowing an administrator to specify alternate
ports, vnis and outgoing interfaces for VXLAN device forwarding tables.

Changes since v3: changed NDA_PORT to be 16-bit network byte order to match
	changed byte-order/size in the VXLAN driver.
Signed-Off-By: David L Stevens <dlstevens@us.ibm.com>