anv, iris: Avoid sampling some MCS surfaces with clear
On TGL, the sampler has an issue with some 8 and 16bpp MSAA fast clears. See HSD 1707282275 and 14013111325 for more information.
This supposedly avoids a GPU hang on BF4, but I haven't tested the game nor have I been able to personally confirm that this helps any specific workload.
While working on this, I came across a bug (#4179), possibly in