netlink: move Route type to common arch file

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)

netlink/netlink.go

@@ -0,0 +1,15 @@
+// Packet netlink provide access to low level Netlink sockets and messages.
+//
+// Actual implementations are in:
+// netlink_linux.go
+// netlink_darwin.go
+package netlink
+
+import "net"
+
+// A Route is a subnet associated with the interface to reach it.
+type Route struct {
+	*net.IPNet
+	Iface   *net.Interface
+	Default bool
+}