net/mlx5: fw_tracer, Add support for strings DB update event

In case a new string DB is added to the FW, the FW publishes an event
notifying the strings DB have updated.

Add support in driver for handling this event.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>