scsi: ipr: Fix WARNING in ipr_init()

ipr_init() will not call unregister_reboot_notifier() when
pci_register_driver() fails, which causes a WARNING. Call
unregister_reboot_notifier() when pci_register_driver() fails.

notifier callback ipr_halt [ipr] already registered
WARNING: CPU: 3 PID: 299 at kernel/notifier.c:29
notifier_chain_register+0x16d/0x230
Modules linked in: ipr(+) xhci_pci_renesas xhci_hcd ehci_hcd usbcore
led_class gpu_sched drm_buddy video wmi drm_ttm_helper ttm
drm_display_helper drm_kms_helper drm drm_panel_orientation_quirks
agpgart cfbft
CPU: 3 PID: 299 Comm: modprobe Tainted: G        W
6.1.0-rc1-00190-g39508d23b672-dirty #332
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:notifier_chain_register+0x16d/0x230
Call Trace:
 <TASK>
 __blocking_notifier_chain_register+0x73/0xb0
 ipr_init+0x30/0x1000 [ipr]
 do_one_initcall+0xdb/0x480
 do_init_module+0x1cf/0x680
 load_module+0x6a50/0x70a0
 __do_sys_finit_module+0x12f/0x1c0
 do_syscall_64+0x3f/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: f72919ec2b ("[SCSI] ipr: implement shutdown changes and remove obsolete write cache parameter")
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Link: https://lore.kernel.org/r/20221113064513.14028-1-shangxiaojing@huawei.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ipr.c

@@ -10872,11 +10872,19 @@ static struct notifier_block ipr_notifier = {
  **/
 static int __init ipr_init(void)
 {
+	int rc;
+
 	ipr_info("IBM Power RAID SCSI Device Driver version: %s %s\n",
 		 IPR_DRIVER_VERSION, IPR_DRIVER_DATE);
 
 	register_reboot_notifier(&ipr_notifier);
-	return pci_register_driver(&ipr_driver);
+	rc = pci_register_driver(&ipr_driver);
+	if (rc) {
+		unregister_reboot_notifier(&ipr_notifier);
+		return rc;
+	}
+
+	return 0;
 }
 
 /**