staging: rtl8192u: r8192U_wx: use netdev_warn() instead of printk()

printk() is deprecated, use netdev_warn() instead, which is a message printing
function specific for network devices.
Issue found by checkpatch.
Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Suggested-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Lourdes Pedrajas <lu@pplo.net>
Link: https://lore.kernel.org/r/20200317165917.6260-1-lu@pplo.netSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r8192U_wx.c

@@ -588,7 +588,7 @@ static int r8192_wx_set_enc(struct net_device *dev,
 				hwkey);                 /* KeyContent */
 
 		} else {
-			printk("wrong type in WEP, not WEP40 and WEP104\n");
+			netdev_warn(dev, "wrong type in WEP, not WEP40 and WEP104\n");
 		}
 
 	}