staging: gdm724x: 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/gdm724x/gdm_lte.c

@@ -889,7 +889,7 @@ int register_lte_device(struct phy_dev *phy_dev,
 		/* Allocate netdev */
 		net = alloc_netdev(sizeof(struct nic), pdn_dev_name,
 				   NET_NAME_UNKNOWN, ether_setup);
-		if (net == NULL) {
+		if (!net) {
 			pr_err("alloc_netdev failed\n");
 			ret = -ENOMEM;
 			goto err;