Rename au921 to au915

[frazar]

Closes #363

Currently it fails in CI because, for the MCCI Catena's BSP, the lorawan_region parameter is named au921, not au915.

The error is the following:

$ _notstm32l0 ||  arduino --verify --board $(_stm32l0opts '' au915  ) $MCCI_STM32_OPTS $PWD/examples/raw-feather/raw-feather.ino

Picked up JAVA_TOOL_OPTIONS: 
Loading configuration...
Initializing packages...
Preparing boards...
Error: au915: Invalid value for option "lorawan_region" for board "mcci_catena_4551"
The command "_notstm32l0 ||  arduino --verify --board $(_stm32l0opts '' au915  ) $MCCI_STM32_OPTS $PWD/examples/raw-feather/raw-feather.ino" exited with 3.

It should be fixed if mcci-catena/ArduinoCore-samd#37 is merged.

[terrillmoore]

Ah, sorry, and thanks for this.

I want to make sure I understand: are you expecting the CI build to fail for this even after the patch?

I think it might be a good idea to have some transitional code.

If there's no CFG_* defined in the "standard" set, then check CFG_au921. If it's defined, define CFG_au915, and go on; otherwise define CFG_eu866 as at present. Would that allow us to work either way, transitionally?

[frazar]

To clarify, this should work after mcci-catena/ArduinoCore-samd#37 is merged.
It fails only beacuse it passes the value "au915" for the parameter "lorawan_region" of the BSP. Since as of now the BSP is (mistakenly) naming the configuration "au921", it fails.