intel/blorp: Allow LOD0 fast-clears with HiZ WT

I did some more debugging of this feature, but this time with a modified
version of the piglit test, ./bin/depthstencil-render-miplevels.
I modified the test to:

* Control which LOD to stop populating/clearing
* Print out the results of readpixels to stderr

From there, I could see how different surface dimensions affected
fast-clears. Depending on the surface dimensions, fast-clearing an LOD
above the LOD0 could cause other LODs to be cleared and/or cause the
targeted LOD to be only partially cleared (for example, when the LOD0
dimension is 66x66 and the test doesn't clear LOD3+). This never happens
when fast-clearing LOD0 however.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5258
Reviewed-by: Rohan Garg <rohan.garg@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30250>

src/intel/blorp/blorp_clear.c

@@ -982,7 +982,7 @@ blorp_can_hiz_clear_depth(const struct intel_device_info *devinfo,
                               x1 % 16 || y1 % 8);
       const bool partial_clear = x0 > 0 || y0 > 0 || !max_x1_y1;
 
-      if (unaligned && (partial_clear || surf->levels > 1))
+      if (unaligned && (partial_clear || level > 0))
          return false;
    }