staging: rtl8192u: remove redundant nul check on pointer dev

There is a null check on pointer dev which implies it may be null, however
dev can never be null as it is set in rtl8192_usb_probe via the call
to usb_set_intfdata.

Detected by CoverityScan, CID#143078 ("Dereference after null check")

Fixes: 8fc8598e ("Staging: Added Realtek rtl8192u driver to staging")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/r8192U_core.c

@@ -4957,11 +4957,9 @@ static void rtl8192_usb_disconnect(struct usb_interface *intf)
 	struct net_device *dev = usb_get_intfdata(intf);
 	struct r8192_priv *priv = ieee80211_priv(dev);
 
-	if (dev) {
 	unregister_netdev(dev);
 
-		RT_TRACE(COMP_DOWN,
-			 "=============>wlan driver to be removed\n");
+	RT_TRACE(COMP_DOWN, "=============>wlan driver to be removed\n");
 	rtl8192_proc_remove_one(dev);
 
 	rtl8192_down(dev);
@@ -4969,8 +4967,8 @@ static void rtl8192_usb_disconnect(struct usb_interface *intf)
 	priv->pFirmware = NULL;
 	rtl8192_usb_deleteendpoints(dev);
 	usleep_range(10000, 11000);
-	}
 	free_ieee80211(dev);
+
 	RT_TRACE(COMP_DOWN, "wlan driver removed\n");
 }