* Support auto-detect of HDLC on MSP430

Use USER_BOOT (15) as output, held low to signal HDLC mode
Repeat send and pulse USER_BOOT until HDLC ACK received
Update README

Also add increased drive strength for USER_BOOT pins, to be included
in zephyr at some point.

* Add hooks for console
* Switch to memory slab for HDLC frames
* Use fixed buffer for UART receive
* Use HDLC I-Frames for WPAN packets to host
* Add LED1 blink on TX, LED2 blink on RX.
* Cleanup printk/debug messages
* Use beagleconnect_freedom board

Working gateway application

Apply set channel on start
Additional debug info
Add application options to Kconfig
Updated board config
Updated logging
Use single buffer fragment for radio send
Add overlay for subghz
Update instructions

Signed-off-by: Erik Larson <erik@statropy.com>

tx error ignored for now