kms plugin: use first returned mode if no preferred one is present

The list of returned modes is scanned for the first one marked as
preferred, and that is used. If no preferred mode was found then the
builtin default mode of 1024x768 is used. Use that builtin mode only if
no modes were returned at all, pick the first one if any were returned.

Change-Id: Ib355cc92219ced093c605f49dae4e34ff244b639
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/plugins/platforms/kms/qkmsscreen.cpp

@@ -124,8 +124,12 @@ void QKmsScreen::initializeScreenMode(const drmModeRes *resources, const drmMode
             break;
         }
     }
-    if (!mode)
-        mode = &builtin_1024x768;
+    if (!mode) {
+        if (connector->count_modes > 0)
+            mode = &connector->modes[0];
+        else
+            mode = &builtin_1024x768;
+    }
 
     drmModeEncoder *encoder = drmModeGetEncoder(m_device->fd(), connector->encoders[0]);
     if (encoder == 0)