Fix premultiplied image format check

Check the QPixelFormat instead of relying on an easily outdated list of
formats.

Change-Id: I076391ac22bc9d4e70e53232c529d09d7aab13b9
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
(cherry picked from commit fdc29cf)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/gui/painting/qpaintengine_raster.cpp

@@ -2221,21 +2221,11 @@ void QRasterPaintEngine::drawImage(const QRectF &r, const QImage &img, const QRe
 
         // Do whatever fillRect() does, but without premultiplying the color if it's already premultiplied.
         QRgb color = img.pixel(sr_l, sr_t);
-        switch (img.format()) {
-        case QImage::Format_ARGB32_Premultiplied:
-        case QImage::Format_ARGB8565_Premultiplied:
-        case QImage::Format_ARGB6666_Premultiplied:
-        case QImage::Format_ARGB8555_Premultiplied:
-        case QImage::Format_ARGB4444_Premultiplied:
-        case QImage::Format_RGBA8888_Premultiplied:
-        case QImage::Format_A2BGR30_Premultiplied:
-        case QImage::Format_A2RGB30_Premultiplied:
+        if (img.pixelFormat().premultiplied() == QPixelFormat::Premultiplied) {
             // Combine premultiplied color with the opacity set on the painter.
             d->solid_color_filler.solidColor = multiplyAlpha256(QRgba64::fromArgb32(color), s->intOpacity);
-            break;
-        default:
+        } else {
             d->solid_color_filler.solidColor = qPremultiply(combineAlpha256(QRgba64::fromArgb32(color), s->intOpacity));
-            break;
         }
 
         if (d->solid_color_filler.solidColor.alphaF() <= 0.0f && s->composition_mode == QPainter::CompositionMode_SourceOver)