anv,iris: Make the D16 reg mode single-sampled
Wa_14010455700 is dependent on the format and sample count, but our code to track whether or not it had been applied was only dependent on the format.
As a result, we failed to enable the workaround when an app used a D16 2xMSAA buffer, then a D16 1xMSAA buffer right afterwards.
Make the workaround tracking code sample-dependent to fix this.
This fixes an issue introduced in !11454 (merged) but doesn't apply cleanly due to !17778 (merged). So, I've Cc'd stable instead of using the Fixes tag.
/cc @llandwerlin @kwg