net/mlx5: make meter action thread safe

net/mlx5: make meter action thread safe

This commit adds the spinlock for the meter action to make it be thread
safe. Atomic reference counter in all is not enough as the meter action
should be created synchronized with reference counter increment. With
only atomic reference counter, even the counter is increased, the action
may still not be created.

Signed-off-by: Suanming Mou <suanmingm@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>