Renamed A8R8G8B8_2.dds to A8R8G8B8.2.dds.

This fix is needed for further patch to be able to get image format
(subtype) from filename.

Change-Id: I0de72be6c8d1942e6ad63c4d131bd380379a5417
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>