freedreno/gmem: Fix for partial z/s fast-clear
If we have a combined depth+stencil buffer, but fast-clear just one of the two channels, we need to mark the other as needing restore.
fixes a bug I noticed w/ stk over the weekend, but couldn't debug at the time due to lack of renderdoc setup (apitrace isn't really great for tracking down these sorts of issues). Not sure why it doesn't show up in the stk traces we have in CI, probably they are from an older version of stk?