drivers/net/wireless/ipw2x00/libipw_module.c: remove unnecessary null test before kfree

Fix checkpatch warning:
WARNING: kfree(NULL) is safe this check is probably not required

Cc: Stanislav Yakovlev <stas.yakovlev@gmail.com>
Cc: "John W. Linville" <linville@tuxdriver.com>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ipw2x00/libipw_module.c

@@ -100,8 +100,7 @@ static inline void libipw_networks_free(struct libipw_device *ieee)
 	int i;
 
 	for (i = 0; i < MAX_NETWORK_COUNT; i++) {
-		if (ieee->networks[i]->ibss_dfs)
-			kfree(ieee->networks[i]->ibss_dfs);
+		kfree(ieee->networks[i]->ibss_dfs);
 		kfree(ieee->networks[i]);
 	}
 }