a first comment: you seem to be using the 'older' initial manifest that I created to get started. We now have more 'official' OpenEmbedded images using what we call the OE Reference Platform Build (oe-rpb), the wiki page that you probably followed initially has been updated accordingly:
So I would recommend to switch over, just to make sure you are tracking what we are working on.
That said, for your specific issue, this is the expected behavior, the interface is not automatically started. Keep in mind that you are building a minimal system, unlike a full fledge 'desktop' (like we release based on Debian).
To check if the wlan interface exists, you can run:
$ ip link
and it should be visible, but DOWN.
To start it up:
$ ip link set wlan0 up
then you can check it is functional by scanning networks around you:
$ iw wlan0 scan