copybit: Ensure that copybit is not generating alpha values

When image was being up scaled beyond 4 times and intermediate
buffer is used, alpha value would be 0 in intermediate buffer.
This would then be blitted onto final buffer that contained alpha
value. Since fg had alpha value of 0 entire image would be blended
out.

Change-Id: I6daf03e93719212ee597c218655ae8692ae79e72
1 file changed