net/mlx5: add meter hierarchy destroy and cleanup

net/mlx5: add meter hierarchy destroy and cleanup

When creating hierarchy meter, its color rules will increase next
meter's reference count, so when destroy the hierarchy meter, also
need to dereference the next meter's count.

During flushing all meters of a port, need to destroy all hierarchy
meters and their policies first, to dereference the last meter in
hierarchy. Then all meters have no reference and can be destroyed.

Signed-off-by: Shun Hao <shunh@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>