iwlwifi: mvm: Fix channel switch in case of count <= 1

The code did not consider the case that the channel switch counter
is <= 1, which would result with an inaccurate calculation of the
time event apply time.

As the specification states that in case of counter == 0 the switch
occurs at any time after the reception the frame, and for counter == 1
the switch would happens before the next TBTT, schedule the time
event immediately.
Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c

@@ -3875,11 +3875,16 @@ static int iwl_mvm_pre_channel_switch(struct ieee80211_hw *hw,
 
 		/* Schedule the time event to a bit before beacon 1,
 		 * to make sure we're in the new channel when the
-		 * GO/AP arrives.
+		 * GO/AP arrives. In case count <= 1 immediately schedule the
+		 * TE (this might result with some packet loss or connection
+		 * loss).
 		 */
-		apply_time = chsw->device_timestamp +
-			((vif->bss_conf.beacon_int * (chsw->count - 1) -
-			  IWL_MVM_CHANNEL_SWITCH_TIME_CLIENT) * 1024);
+		if (chsw->count <= 1)
+			apply_time = 0;
+		else
+			apply_time = chsw->device_timestamp +
+				((vif->bss_conf.beacon_int * (chsw->count - 1) -
+				  IWL_MVM_CHANNEL_SWITCH_TIME_CLIENT) * 1024);
 
 		if (chsw->block_tx)
 			iwl_mvm_csa_client_absent(mvm, vif);