anv: fix descriptor pool leak in VMA object
Quoting the spec :
"When a pool is destroyed, all descriptor sets allocated from the pool are implicitly freed and become invalid. Descriptor sets allocated from a given pool do not need to be freed before destroying that descriptor pool."
This implies we might leak nodes allocated in the vma object.
Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Fixes: 0a6d2593 ("anv: Allocate descriptor buffers from the BO cache")