ottercast-amp-v0.0.1

board: otter: add intial OtterCast Amp support

This commit adds initial support for the Ottercast Amp.
Ultimately the goal is to have a unified firmware image for both the
Ottercast Audio and the OtterCast Amp

v0.0.2

Update Buildroot to 2020.11.3

v0.0.1

github: compress sdcard image file