phage: cmd-radio: Remove non-comand-related stuff

Radio code gets moved to its own file.
phage: radio: Add phage-radio module

This module has some SPI issues still, but it works.  More or less.
phage: events: Add radio event support

There are three interrupts: One for Carrier Detect, one for Address
Matched, and one for Data Received.
phage: Add radio support to main.c