Don't restore terminal settings on close

The API for controlling the terminal settings restoration was
deprecated in 5.3, and removed in 6. However, the underlying
code that restores the settings was not removed as planned. This
commit removes the code that was connected to the deprecated API
function.

src/serialport/qserialport_p.h

@@ -187,9 +187,7 @@ class QSerialPortPrivate : public QIODevicePrivate
 
     void emitReadyRead();
 
-    DCB restoredDcb;
     COMMTIMEOUTS currentCommTimeouts;
-    COMMTIMEOUTS restoredCommTimeouts;
     HANDLE handle = INVALID_HANDLE_VALUE;
     QByteArray readChunkBuffer;
     QByteArray writeChunkBuffer;
@@ -233,7 +231,6 @@ class QSerialPortPrivate : public QIODevicePrivate
     bool startAsyncWrite();
     bool completeAsyncWrite();
 
-    struct termios restoredTermios;
     int descriptor = -1;
 
     QSocketNotifier *readNotifier = nullptr;

src/serialport/qserialport_unix.cpp

@@ -321,9 +321,6 @@ bool QSerialPortPrivate::open(QIODevice::OpenMode mode)
 
 void QSerialPortPrivate::close()
 {
-    if (settingsRestoredOnClose)
-        ::tcsetattr(descriptor, TCSANOW, &restoredTermios);
-
 #ifdef TIOCNXCL
     ::ioctl(descriptor, TIOCNXCL);
 #endif
@@ -835,8 +832,6 @@ inline bool QSerialPortPrivate::initialize(QIODevice::OpenMode mode)
     if (!getTermios(&tio))
         return false;
 
-    restoredTermios = tio;
-
     qt_set_common_props(&tio, mode);
     qt_set_databits(&tio, dataBits);
     qt_set_parity(&tio, parity);

src/serialport/qserialport_win.cpp

@@ -177,11 +177,6 @@ void QSerialPortPrivate::close()
     writeStarted = false;
     writeBuffer.clear();
 
-    if (settingsRestoredOnClose) {
-        ::SetCommState(handle, &restoredDcb);
-        ::SetCommTimeouts(handle, &restoredCommTimeouts);
-    }
-
     ::CloseHandle(handle);
     handle = INVALID_HANDLE_VALUE;
 }
@@ -631,8 +626,6 @@ inline bool QSerialPortPrivate::initialize(QIODevice::OpenMode mode)
     if (!getDcb(&dcb))
         return false;
 
-    restoredDcb = dcb;
-
     qt_set_common_props(&dcb);
     qt_set_baudrate(&dcb, inputBaudRate);
     qt_set_databits(&dcb, dataBits);
@@ -643,11 +636,6 @@ inline bool QSerialPortPrivate::initialize(QIODevice::OpenMode mode)
     if (!setDcb(&dcb))
         return false;
 
-    if (!::GetCommTimeouts(handle, &restoredCommTimeouts)) {
-        setError(getSystemError());
-        return false;
-    }
-
     ::ZeroMemory(&currentCommTimeouts, sizeof(currentCommTimeouts));
     currentCommTimeouts.ReadIntervalTimeout = MAXDWORD;