Do not activate embedded mode for wayland

Embedded (fullscreen) mode was activated automatically if QPA
platform type is eglfs, wayland or linuxfb.
However although setting window size to -1 does result in fullscreen
on eglfs, on wayland it results in
"Client tried to set invalid geometry"

Do not activate embedded mode for wayland.

Closes #143

imagewriter.cpp

@@ -46,7 +46,7 @@ ImageWriter::ImageWriter(QObject *parent)
     connect(&_polltimer, SIGNAL(timeout()), SLOT(pollProgress()));
 
     QString platform = QGuiApplication::platformName();
-    if (platform == "eglfs" || platform == "wayland" || platform == "linuxfb")
+    if (platform == "eglfs" || platform == "linuxfb")
     {
         _embeddedMode = true;
         connect(&_networkchecktimer, SIGNAL(timeout()), SLOT(pollNetwork()));