gallium/auxiliary/vl: Fix transparent issue on compute shader with rgba

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109646
Problem 1,4: they are caused by imcomplete blend comute shader
implementation. So Reverts rgba back to frament shader.

Fixes: 9364d66cb7f7 (Add video compositor compute shader render)
Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Tested-by: Bruno Milreu <bmilreu@gmail.com>
1 file changed