Staging: rtl8712: Clean up tests if NULL returned on failure

Some functions like kmalloc/usb_alloc_urb/kmalloc_array returns 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
by these functions 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>
diff --git a/drivers/staging/rtl8712/rtl871x_sta_mgt.c b/drivers/staging/rtl8712/rtl871x_sta_mgt.c
index 3fe45b6..e90c00d 100644
--- a/drivers/staging/rtl8712/rtl871x_sta_mgt.c
+++ b/drivers/staging/rtl8712/rtl871x_sta_mgt.c
@@ -53,7 +53,7 @@
 
 	pstapriv->pallocated_stainfo_buf = kmalloc(sizeof(struct sta_info) *
 						   NUM_STA + 4, GFP_ATOMIC);
-	if (pstapriv->pallocated_stainfo_buf == NULL)
+	if (!pstapriv->pallocated_stainfo_buf)
 		return _FAIL;
 	pstapriv->pstainfo_buf = pstapriv->pallocated_stainfo_buf + 4 -
 		((addr_t)(pstapriv->pallocated_stainfo_buf) & 3);