EthernetInterface: Mark Speed and AutoNeg as readonly

These values are read from ethtool ioctl and cannot be modified in
networkd, mark them as readonly.

Change-Id: I5df264c64dc82ca61f53b05a36762b30b4f4810f
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 f382ee1..c308748 100644
--- a/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
+++ b/yaml/xyz/openbmc_project/Network/EthernetInterface.interface.yaml
@@ -10,10 +10,14 @@
           Name of the ethernet interface.
     - name: Speed
       type: uint32
+      flags:
+          - readonly
       description: >
           Current speed of the ethernet interface, in Mbps.
     - name: AutoNeg
       type: boolean
+      flags:
+          - readonly
       description: >
           This indicates if the speed and duplex are automatically negotiated
           and configured on this ethernet interface.