Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/vishvananda/netlink/nl/bridge_linux.go

@@ -0,0 +1,74 @@
+package nl
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+const (
+	SizeofBridgeVlanInfo = 0x04
+)
+
+/* Bridge Flags */
+const (
+	BRIDGE_FLAGS_MASTER = iota /* Bridge command to/from master */
+	BRIDGE_FLAGS_SELF          /* Bridge command to/from lowerdev */
+)
+
+/* Bridge management nested attributes
+ * [IFLA_AF_SPEC] = {
+ *     [IFLA_BRIDGE_FLAGS]
+ *     [IFLA_BRIDGE_MODE]
+ *     [IFLA_BRIDGE_VLAN_INFO]
+ * }
+ */
+const (
+	IFLA_BRIDGE_FLAGS = iota
+	IFLA_BRIDGE_MODE
+	IFLA_BRIDGE_VLAN_INFO
+)
+
+const (
+	BRIDGE_VLAN_INFO_MASTER = 1 << iota
+	BRIDGE_VLAN_INFO_PVID
+	BRIDGE_VLAN_INFO_UNTAGGED
+	BRIDGE_VLAN_INFO_RANGE_BEGIN
+	BRIDGE_VLAN_INFO_RANGE_END
+)
+
+// struct bridge_vlan_info {
+//   __u16 flags;
+//   __u16 vid;
+// };
+
+type BridgeVlanInfo struct {
+	Flags uint16
+	Vid   uint16
+}
+
+func (b *BridgeVlanInfo) Serialize() []byte {
+	return (*(*[SizeofBridgeVlanInfo]byte)(unsafe.Pointer(b)))[:]
+}
+
+func DeserializeBridgeVlanInfo(b []byte) *BridgeVlanInfo {
+	return (*BridgeVlanInfo)(unsafe.Pointer(&b[0:SizeofBridgeVlanInfo][0]))
+}
+
+func (b *BridgeVlanInfo) PortVID() bool {
+	return b.Flags&BRIDGE_VLAN_INFO_PVID > 0
+}
+
+func (b *BridgeVlanInfo) EngressUntag() bool {
+	return b.Flags&BRIDGE_VLAN_INFO_UNTAGGED > 0
+}
+
+func (b *BridgeVlanInfo) String() string {
+	return fmt.Sprintf("%+v", *b)
+}
+
+/* New extended info filters for IFLA_EXT_MASK */
+const (
+	RTEXT_FILTER_VF = 1 << iota
+	RTEXT_FILTER_BRVLAN
+	RTEXT_FILTER_BRVLAN_COMPRESSED
+)