Inside poky distro (.../poky/meta/recipes-connectivity):
[user@localhost recipes-connectivity]$ pwd
/home/user/YOCTO/oe_core_embedded/poky/meta/recipes-connectivity
[user@localhost recipes-connectivity]$ ls -al
total 96
drwxrwxr-x. 24 user user 4096 Oct 18 12:49 .
drwxrwxr-x. 19 user user 4096 Nov 18 15:13 ..
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 avahi
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 bind
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 bluez5
drwxrwxr-x. 5 user user 4096 Oct 18 12:49 connman
drwxrwxr-x. 4 user user 4096 Oct 18 12:49 dhcp
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 iproute2
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 irda-utils
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 iw
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 libnss-mdns
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 libpcap
drwxrwxr-x. 2 user user 4096 Oct 18 12:49 mobile-broadband-provider-info
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 neard
drwxrwxr-x. 5 user user 4096 Oct 18 12:49 nfs-utils
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 ofono
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 openssh
drwxrwxr-x. 4 user user 4096 Oct 18 12:49 openssl
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 ppp
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 ppp-dialin
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 resolvconf
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 socat
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 wireless-tools
drwxrwxr-x. 3 user user 4096 Oct 18 12:49 wpa-supplicant
[user@localhost recipes-connectivity]$
IMAGE_INSTALL_append += "rfkill" (my best guess, easiest way).