scripts: runners: bossac: Change speed by protocol

Add is_extended_samba_protocol method to verify if board is using SAM-BA
extended protocol (Arduino/Adafruit UF2).  It allows enforce serial line
speed to 1200 baud automatically.  This avoid add entries on board.cmake
file.

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>