Remove catchall receive and return errors from port
Remove catchall receive and return errors from port

This fixes an issue when multiple processes call SPI.transfer. The
catchall receive incorrectly handles a GenServer.call message and this
causes an exception.

Thanks to sandromehic for finding the issue and providing an easy way to
reproduce. See https://github.com/fhunleth/elixir_ale/issues/53.

fhunleth/elixir_ale