* DI layout is identified by attempting to read OUI from both layouts
* MSC address is passed to flashstub in r3
Retested EZR32LG230 (EZR Leopard Gecko M3)
Tested EFR32BG13P532F512GM32 (EFR Blue Gecko)
Achieves aims of PR #264 (I think) Thanks to @dholth and @ryankurte for inspiration
Fixes Issue #226