The only depth/stencil aux usage that can actually use the BO is
ISL_AUX_USAGE_HIZ_CCS_WT. Even with that aux usage, iris may disable
sampling depending on the surface configuration.
Allocate the clear color BO when it'd be usable, not just when the
auxiliary surface size is non-zero on ICL+. This prepares for CCS on
XeHP, which won't have an auxiliary surface.
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13555>