ubi: Fix ubi_init() ubiblock_exit() section mismatch

Since ubiblock_exit() is now called from an init function,
the __exit section no longer makes sense.

Cc: Ben Hutchings <bwh@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407131403.wZJpd8n2-lkp@intel.com/Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>

drivers/mtd/ubi/block.c

@@ -670,7 +670,7 @@ int __init ubiblock_init(void)
 	return ret;
 }
 
-void __exit ubiblock_exit(void)
+void ubiblock_exit(void)
 {
 	ubi_unregister_volume_notifier(&ubiblock_notifier);
 	ubiblock_remove_all();