[bug report] iwlwifi: dbg: support multiple dumps in legacy dump flow

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Shahar S Matityahu,

This is a semi-automatic email about new static checker warnings.

The patch 7a99c877ae8e: "iwlwifi: dbg: support multiple dumps in 
legacy dump flow" from Apr 17, 2020, leads to the following Smatch 
complaint:

    drivers/net/wireless/intel/iwlwifi/fw/dbg.c:2182 iwl_fw_free_dump_desc()
    error: we previously assumed 'desc' could be null (see line 2179)

drivers/net/wireless/intel/iwlwifi/fw/dbg.c
  2178	{
  2179		if (desc && *desc != &iwl_dump_desc_assert)
                    ^^^^
New check for NULL

  2180			kfree(*desc);
  2181	
  2182		*desc = NULL;
                ^^^^^
New unchecked dereference.

  2183		fwrt->dump.lmac_err_id[0] = 0;
  2184		if (fwrt->smem_cfg.num_lmacs > 1)

regards,
dan carpenter