samples: usb: wpanusb: add MCR20A overlay config
Add support for NXP MCR20A 802.15.4 module as an overlay config file.
Use this file like so:
cmake -DBOARD=usb_kw24d512 \
-DOVERLAY_CONFIG=overlay-mcr20a.conf ..
Signed-off-by: Michael Scott <mike@foundries.io>