Staging: gdm72xx: use !x instead of x == NULL

Functions like devm_kzalloc, kmalloc_array, devm_ioremap,
usb_alloc_urb, alloc_netdev return NULL as a return value on failure.
Generally, When NULL represents failure, !x is commonly used.

This patch cleans up the tests on the results of these functions, thereby
using !x instead of x == NULL or NULL == x. This is done via following
coccinelle script:
@prob_7@
identifier x;
statement S;
@@

(
 x = devm_kzalloc(...);
|
 x = usb_alloc_urb(...);
|
 x = kmalloc_array(...);
|
 x = devm_ioremap(...);
|
 x = alloc_netdev(...);
)
 ...
- if(NULL == x)
+ if(!x)
        S
Further we have used isomorphism characteristics of coccinelle to
indicate x == NULL and NULL == x are equivalent. This is done via
following iso script.

Expression
@ is_null @ expression X; @@
X == NULL <=> NULL == X

Signed-off-by: Somya Anand <somyaanand214@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gdm72xx/gdm_wimax.c

@@ -749,7 +749,7 @@ int register_wimax_device(struct phy_dev *phy_dev, struct device *pdev)
 	dev = alloc_netdev(sizeof(*nic), "wm%d", NET_NAME_UNKNOWN,
 			   ether_setup);
 
-	if (dev == NULL) {
+	if (!dev) {
 		pr_err("alloc_etherdev failed\n");
 		return -ENOMEM;
 	}