iOS: use 'self' rather than 'super' pointer in initWithQIOSWindow

If we use super, our own initWithFrame override will never be
called.

Change-Id: I606beb653239cdfc46f41db4ec0791dfa5d4edea
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>

src/plugins/platforms/ios/qioswindow.mm

@@ -72,7 +72,7 @@ static QRect fromCGRect(const CGRect &rect)
 
 -(id)initWithQIOSWindow:(QIOSWindow *)window
 {
-    if (self = [super initWithFrame:toCGRect(window->geometry())])
+    if (self = [self initWithFrame:toCGRect(window->geometry())])
         m_qioswindow = window;
 
     return self;