asahi: Rename no colour output to tag write disable
Comparison with PowerVR's XML shows that this is the actual name... And it needs to be set a bit more carefully than "no colour output" in order to get correct behaviour for depth-only passes that use sample mask / discard. Fix the name first, the extra conditions will come when they're needed for multisampling.
Signed-off-by: Alyssa Rosenzweig alyssa@rosenzweig.io