Refactor the speed configuration for *nix

The internal implementation of this is a little tangled. It is
reasonable to simplify it:

1. Remove the setBaudRate_helper() method, as it is equivalent to
   setStandardBaudRate() method.

2. Now the setStandardBaudRate() and the setCustomBaudRate() are
   self-sufficient methods (can setup a speed and an error codes
   internally) and return a boolean values.

Also added the "loopback" test for check of different speeds.

Tested with the on-board and the USB serial ports.

Change-Id: I4320c2e29ad42a394e07753cbaea804d0faf6b78
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>

0 files changed, 0 insertions, 0 deletions