mm: memfd_luo: restore and free memfd_luo_ser on failure

mm: memfd_luo: restore and free memfd_luo_ser on failure

memfd_luo_ser has the serialization metadata.  It is of no use once
restoration fails.  Free it on failure.

Link: https://lkml.kernel.org/r/20260122151842.4069702-4-pratyush@kernel.org
Fixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd")
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>