If the driver is unloaded when D3 debug data pulling is enabled
but not triggered, it doesn't release the data buffer.

Fix this by adding iwl_fw_runtime_free and calling it from the
relevant places.

Fixes: 2d8c2615 ("iwlwifi: add d3 debug data support")
Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>