Ensure both input and output baud rates are set.

QSerialPortPrivate::setBaudRate() wasn't trying to set the output
baud rate for the port after successfully setting the input baud rate.

Also, some devices (such as FTDI chips) on Mac don't respond
properly if you call updateTermios() with mismatched baud rates,
even if you later set them to be the same.

Change-Id: I507fe10cba221bb4e43ded650dc44cc974de2414
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Laszlo Papp <lpapp@kde.org>
Fix setting custom baud rates under Linux

This regression was caused by 7c737e0edcb93585856c65890ef34e5c5a28ee6b.
The initialization of the (current) serial port info was removed in that commit.

Tested on Linux x86_64 with Qt 5.1.1 and 4.8.6.

Task-number: QTBUG-38961
Change-Id: Idd3c5dc7eb37093848f33387563ff14567ac54fe
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>