net/mlx5: fw_tracer, Clear load bit when freeing string DBs buffers

Whenever the driver is reading the string DBs into buffers, the driver
is setting the load bit, but the driver never clears this bit.
As a result, in case load bit is on and the driver query the device for
new string DBs, the driver won't read again the string DBs.
Fix it by clearing the load bit when query the device for new string
DBs.

Fixes: 2d693567

 ("net/mlx5: Add support for fw live patch event")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>