Change the interface type

[wungad]

Interfaces that have physical presence on the system must be treated as iana-if-type:ethernetCsmacd.
VLAN sub-interfaces created on their respective parent interfaces must be treated as iana-if-tyepe:l2vlan. They must also have ietf-if-extensions:parent-interface node that identifies the parent interface name. Currently both are parsed as iana-if-type:ethernetCsmacd.

Example for vlan sub-interface net1.90 below:

<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
  <interface>
    <name>net1.90</name>
    <type xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">ianaift:l2vlan</type>
    <enabled>true</enabled>
    <parent-interface xmlns="urn:ietf:params:xml:ns:yang:ietf-if-extensions">net1</parent-interface>
    <encapsulation xmlns="urn:ietf:params:xml:ns:yang:ietf-if-extensions">
        <dot1q-vlan xmlns="urn:ietf:params:xml:ns:yang:ietf-if-vlan-encapsulation">
            <outer-tag>
                <tag-type xmlns:dot1q-types="urn:ieee:std:802.1Q:yang:ieee802-dot1q-types" >dot1q-types:s-vlan</tag-type>
                <vlan-id>90</vlan-id>
            </outer-tag>
        </dot1q-vlan>
    </encapsulation">

  </interface>
</interfaces>

[precla]

created MR: #8

please test