CVE-2024-40969 f2fs: don't set RO when shutting down f2fs

In the Linux kernel, the following vulnerability has been resolved:

f2fs: don’t set RO when shutting down f2fs

Shutdown does not check the error of thaw_super due to readonly, which
causes a deadlock like below.

f2fs_ioc_shutdown(F2FS_GOING_DOWN_FULLSYNC) issue_discard_thread

• bdev_freeze
• freeze_super
• f2fs_stop_checkpoint()
• f2fs_handle_critical_error - sb_start_write
  • set RO - waiting
• bdev_thaw
• thaw_super_locked
  • return -EINVAL, if sb_rdonly()
• f2fs_stop_discard_thread
  -> wait for kthread_stop(discard_thread);