kernel: md: Fix missing release of 'active_io' for flush

In the Linux kernel, the following vulnerability has been resolved: md: Fix missing release of 'activeio' for flush The Linux kernel CVE team has assigned CVE-2024-27023 to this issue. Upstream advisory: https://lore.kernel.org/linux-cve-announce/2024050105-CVE-2024-27023-4810@gregkh/T...