s390/sclp: Fix sclp_init() cleanup on failure

If sclp_init() fails it only partially cleans up: if there are multiple
failing calls to sclp_init() sclp_state_change_event will be added several
times to sclp_reg_list, which results in the following warning:

------------[ cut here ]------------
list_add double add: new=000003ffe1598c10, prev=000003ffe1598bf0, next=000003ffe1598c10.
WARNING: CPU: 0 PID: 1 at lib/list_debug.c:35 __list_add_valid_or_report+0xde/0xf8
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.10.0-rc3
Krnl PSW : 0404c00180000000 000003ffe0d6076a (__list_add_valid_or_report+0xe2/0xf8)
           R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
...
Call Trace:
 [<000003ffe0d6076a>] __list_add_valid_or_report+0xe2/0xf8
([<000003ffe0d60766>] __list_add_valid_or_report+0xde/0xf8)
 [<000003ffe0a8d37e>] sclp_init+0x40e/0x450
 [<000003ffe00009f2>] do_one_initcall+0x42/0x1e0
 [<000003ffe15b77a6>] do_initcalls+0x126/0x150
 [<000003ffe15b7a0a>] kernel_init_freeable+0x1ba/0x1f8
 [<000003ffe0d6650e>] kernel_init+0x2e/0x180
 [<000003ffe000301c>] __ret_from_fork+0x3c/0x60
 [<000003ffe0d759ca>] ret_from_fork+0xa/0x30

Fix this by removing sclp_state_change_event from sclp_reg_list when
sclp_init() fails.

Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Author: hcahca

drivers/s390/char/sclp.c

@@ -1293,6 +1293,7 @@ sclp_init(void)
 fail_unregister_reboot_notifier:
 	unregister_reboot_notifier(&sclp_reboot_notifier);
 fail_init_state_uninitialized:
+	list_del(&sclp_state_change_event.list);
 	sclp_init_state = sclp_init_state_uninitialized;
 	free_page((unsigned long) sclp_read_sccb);
 	free_page((unsigned long) sclp_init_sccb);