wifi: iwlwifi: drop NULL pointer check in iwl_mvm_tzone_set_trip_temp()

Since 'tz_device' is an in-place member of 'struct iwl_mvm', it can't
be NULL and so relevant check may be dropped. Compile tested only.

Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Acked-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20231003092048.24998-1-dmantipov@yandex.ruSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/tt.c

@@ -642,7 +642,6 @@ static int iwl_mvm_tzone_set_trip_temp(struct thermal_zone_device *device,
 				       int trip, int temp)
 {
 	struct iwl_mvm *mvm = thermal_zone_device_priv(device);
-	struct iwl_mvm_thermal_device *tzone;
 	int ret;
 
 	mutex_lock(&mvm->mutex);
@@ -658,12 +657,6 @@ static int iwl_mvm_tzone_set_trip_temp(struct thermal_zone_device *device,
 		goto out;
 	}
 
-	tzone = &mvm->tz_device;
-	if (!tzone) {
-		ret = -EIO;
-		goto out;
-	}
-
 	ret = iwl_mvm_send_temp_report_ths_cmd(mvm);
 out:
 	mutex_unlock(&mvm->mutex);