slLIN v0.4.3

• SAM based boards: remove auto-baud, relax spec

  Auto baud mode is mostly broken in SAMX5X so don't use it.
  See family errata for details.

  Prolong data byte timeout from 1.4 times to 2 times the duration
  of a single byte transmission to work around the frame length jumping
  around for some ECUs.

• Trinket M0: fixes clobbering of PA I/O group