fix several formats for GLES
The VIRGL_FORMAT_A8R8G8B8_UNORM
and VIRGL_FORMAT_X8R8G8B8_UNORM
formats weren't actually taken into account for GLES
The VIRGL_FORMAT_A8R8G8B8_UNORM
and VIRGL_FORMAT_X8R8G8B8_UNORM
formats weren't actually taken into account for GLES