EthernetInterface: Mark InterfaceName and VLANId as const

InterfaceName and VLANId are properties that never change once
initialized, mark them as const.

Change-Id: I0a43c732d8793d3e98666733778f10de23b08640
Signed-off-by: Jiaqing Zhao <jiaqing.zhao@intel.com>
diff --git a/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml b/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
index c308748..096f5b5 100644
--- a/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
+++ b/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
@@ -6,6 +6,8 @@
 properties:
     - name: InterfaceName
       type: string
+      flags:
+          - const
       description: >
           Name of the ethernet interface.
     - name: Speed
diff --git a/yaml/xyz/openbmc_project/Network/VLAN.interface.yaml b/yaml/xyz/openbmc_project/Network/VLAN.interface.yaml
index 873b1b7..e04c36c 100644
--- a/yaml/xyz/openbmc_project/Network/VLAN.interface.yaml
+++ b/yaml/xyz/openbmc_project/Network/VLAN.interface.yaml
@@ -7,9 +7,13 @@
 properties:
     - name: InterfaceName
       type: string
+      flags:
+          - const
       description: >
           Name of the interface.
     - name: Id
       type: uint32
+      flags:
+          - const
       description: >
           VLAN Identifier.