i965/miptree: Fix handling of uninitialized MCS buffers
Before this patch, if we failed to initialize an MCS buffer, we'd
end up in a state in which the miptree thinks it has an MCS buffer,
but doesn't. We also leaked the clear_color_bo if it existed.
With this patch, we now free the miptree aux buffer resources and let
intel_miptree_alloc_mcs() know that the MCS buffer no longer exists.
Reviewed-by: Tapani Pälli <email@example.com>
Reviewed-by: Jason Ekstrand <firstname.lastname@example.org>