net/mlx5: fw_tracer, Fix event handling

mlx5 driver needs to parse traces with event_id inside the range of
first_string_trace and num_string_trace. However, mlx5 is parsing all
events with event_id >= first_string_trace.

Fix it by checking for the correct range.

Fixes: c71ad41c

 ("net/mlx5: FW tracer, events handling")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>