iwlagn: avoid sleep in softirq context

__ieee80211_tasklet_handler -> __ieee80211_rx ->
	__ieee80211_rx_handle_packet -> ieee80211_invoke_rx_handlers ->
	ieee80211_rx_h_decrypt -> ieee80211_crypto_tkip_decrypt ->
	ieee80211_tkip_decrypt_data -> iwl4965_mac_update_tkip_key ->
	iwl_scan_cancel_timeout -> msleep

Ooops!

Avoid the sleep by changing iwl_scan_cancel_timeout with
iwl_scan_cancel and simply returning on failure if the scan persists.
This will cause hardware decryption to fail and we'll handle a few more
frames with software decryption.
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -3252,7 +3252,11 @@ static void iwl4965_mac_update_tkip_key(struct ieee80211_hw *hw,
 		return;
 	}
 
-	iwl_scan_cancel_timeout(priv, 100);
+	if (iwl_scan_cancel(priv)) {
+		/* cancel scan failed, just live w/ bad key and rely
+		   briefly on SW decryption */
+		return;
+	}
 
 	key_flags |= (STA_KEY_FLG_TKIP | STA_KEY_FLG_MAP_KEY_MSK);
 	key_flags |= cpu_to_le16(keyconf->keyidx << STA_KEY_FLG_KEYID_POS);