mac80211_hwsim: Timer should be initialized before device registered

Otherwise if network manager starts configuring Wi-Fi interface
immidiatelly after getting notification of its creation, we will get
NULL pointer dereference:

  BUG: unable to handle kernel NULL pointer dereference at           (null)
  IP: [<ffffffff95ae94c8>] hrtimer_active+0x28/0x50
  ...
  Call Trace:
   [<ffffffff95ae9997>] ? hrtimer_try_to_cancel+0x27/0x110
   [<ffffffff95ae9a95>] ? hrtimer_cancel+0x15/0x20
   [<ffffffffc0803bf0>] ? mac80211_hwsim_config+0x140/0x1c0 [mac80211_hwsim]

Cc: stable@vger.kernel.org
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@globallogic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -2884,6 +2884,10 @@ static int mac80211_hwsim_new_radio(struct genl_info *info,
 
 	wiphy_ext_feature_set(hw->wiphy, NL80211_EXT_FEATURE_CQM_RSSI_LIST);
 
+	tasklet_hrtimer_init(&data->beacon_timer,
+			     mac80211_hwsim_beacon,
+			     CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+
 	err = ieee80211_register_hw(hw);
 	if (err < 0) {
 		pr_debug("mac80211_hwsim: ieee80211_register_hw failed (%d)\n",
@@ -2908,10 +2912,6 @@ static int mac80211_hwsim_new_radio(struct genl_info *info,
 				    data->debugfs,
 				    data, &hwsim_simulate_radar);
 
-	tasklet_hrtimer_init(&data->beacon_timer,
-			     mac80211_hwsim_beacon,
-			     CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
-
 	spin_lock_bh(&hwsim_radio_lock);
 	err = rhashtable_insert_fast(&hwsim_radios_rht, &data->rht,
 				     hwsim_rht_params);