Staging: rtl8192u: Clean up tests if NULL returned on failure

Some functions return Null as their return value on failure. !x is
generally preferred over x==NULL or NULL==x. So make use of !x if
the value returned on failure is NULL.
Done using coccinelle:
@@
expression e;
statement S;
@@
e = \(kmalloc\|devm_kzalloc\|kmalloc_array
     \|devm_ioremap\|usb_alloc_urb\|alloc_netdev\)(...);
- if(e==NULL)
+ if(!e)
  S
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c

@@ -1289,7 +1289,7 @@ int ieee80211_rx(struct ieee80211_device *ieee, struct sk_buff *skb,
 	payload = skb->data + hdrlen;
 	//ethertype = (payload[6] << 8) | payload[7];
 	rxb = kmalloc(sizeof(struct ieee80211_rxb), GFP_ATOMIC);
-	if (rxb == NULL)
+	if (!rxb)
 	{
 		IEEE80211_DEBUG(IEEE80211_DL_ERR,"%s(): kmalloc rxb error\n",__func__);
 		goto rx_dropped;

drivers/staging/rtl8192u/r8192U_core.c

@@ -1732,7 +1732,7 @@ static short rtl8192_usb_initendpoints(struct net_device *dev)
 
 	priv->rx_urb = kmalloc(sizeof(struct urb *) * (MAX_RX_URB + 1),
 			       GFP_KERNEL);
-	if (priv->rx_urb == NULL)
+	if (!priv->rx_urb)
 		return -ENOMEM;
 
 #ifndef JACKSON_NEW_RX