i965/miptree: Zero-initialize CCS_D buffers
Before this patch, the aux_state was actually AUX_INVALID because the BO
was never defined. This was fine on single slice miptrees because we
would fast-clear the resource right after creation. For multi-slice
miptrees on SKL+ however, this results in undefined behavior when
accessing a non-base slice. Here's a specific example:
- Fast clear level 0
- Undefined CCS_D buffer allocated in "PASS_THROUGH" state.
- Level 0 transitions to the CLEAR state.
- Render to level 1
- Level 1 may have a 2-bit pattern of 2's.
- Rendering with a 2 in the CCS is undefined.
Reviewed-by: Jason Ekstrand <email@example.com>