sna/video/sprite: Retry with GPU scaling if setplane fails

The kernel may reject the setplane due to eg. exceeding the max
downscaling limit of the hardware. In that case let's retry the
operation but let the GPU do the scaling for us.

Tested on my IVB, after hacking the kernel to reject setplane
which exceeds the max hw downscaling limit.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>