eglfs: Upload only damaged areas into the textures

Uploading the pixel data for the entire window on every update
is not nice. Not sure why the line in question was added, it is
most likely a leftover from some debugging session.

Change-Id: I161af536c42ac24b299fc674039f2318f0fb8c4f
Reviewed-by: Andy Nichols <andy.nichols@digia.com>

src/platformsupport/eglconvenience/qeglplatformbackingstore.cpp

@@ -93,7 +93,6 @@ void QEGLPlatformBackingStore::updateTexture()
     if (!m_dirty.isNull()) {
         QRegion fixed;
         QRect imageRect = m_image.rect();
-        m_dirty |= imageRect;
 
         foreach (const QRect &rect, m_dirty.rects()) {
             // intersect with image rect to be sure