iwlwifi: pcie: use u32* argument to iwl_trans_get_fw_monitor_len()

That's what we pass, and we don't want/need any negative values.
Found by sparse/smatch.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
1 file changed