zd1211rw: Prefer pr_err over printk error msg

In zd_usb.c usb_init we can prefer pr_err() over printk KERN_ERR
log level.
Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210506044838.GA7260@user

drivers/net/wireless/zydas/zd1211rw/zd_usb.c

@@ -1544,14 +1544,14 @@ static int __init usb_init(void)
 
 	zd_workqueue = create_singlethread_workqueue(driver.name);
 	if (zd_workqueue == NULL) {
-		printk(KERN_ERR "%s couldn't create workqueue\n", driver.name);
+		pr_err("%s couldn't create workqueue\n", driver.name);
 		return -ENOMEM;
 	}
 
 	r = usb_register(&driver);
 	if (r) {
 		destroy_workqueue(zd_workqueue);
-		printk(KERN_ERR "%s usb_register() failed. Error number %d\n",
+		pr_err("%s usb_register() failed. Error number %d\n",
 		       driver.name, r);
 		return r;
 	}