s390/smsgiucv_app: Make use of iucv_alloc_device()

Make use of iucv_alloc_device() to get rid of quite some code. In addition
this also removes a cast to an incompatible function (clang W=1):

  drivers/s390/net/smsgiucv_app.c:176:26: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
    176 |         smsg_app_dev->release = (void (*)(struct device *)) kfree;
        |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/r/20240417-s390-drivers-fix-cast-function-type-v1-2-fd048c9903b0@kernel.orgAcked-by: Alexandra Winter <wintera@linux.ibm.com>
Link: https://lore.kernel.org/r/20240506194454.1160315-5-hca@linux.ibm.comSigned-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

drivers/s390/net/smsgiucv_app.c

@@ -156,25 +156,14 @@ static int __init smsgiucv_app_init(void)
 	if (!MACHINE_IS_VM)
 		return -ENODEV;
 
-	smsg_app_dev = kzalloc(sizeof(*smsg_app_dev), GFP_KERNEL);
-	if (!smsg_app_dev)
-		return -ENOMEM;
-
 	smsgiucv_drv = driver_find(SMSGIUCV_DRV_NAME, &iucv_bus);
-	if (!smsgiucv_drv) {
-		kfree(smsg_app_dev);
+	if (!smsgiucv_drv)
 		return -ENODEV;
-	}
 
-	rc = dev_set_name(smsg_app_dev, KMSG_COMPONENT);
-	if (rc) {
-		kfree(smsg_app_dev);
-		goto fail;
-	}
-	smsg_app_dev->bus = &iucv_bus;
-	smsg_app_dev->parent = iucv_root;
-	smsg_app_dev->release = (void (*)(struct device *)) kfree;
-	smsg_app_dev->driver = smsgiucv_drv;
+	smsg_app_dev = iucv_alloc_device(NULL, smsgiucv_drv, NULL, KMSG_COMPONENT);
+	if (!smsg_app_dev)
+		return -ENOMEM;
+
 	rc = device_register(smsg_app_dev);
 	if (rc) {
 		put_device(smsg_app_dev);