nilfs2: replace vmalloc + copy_from_user with vmemdup_user

nilfs2: replace vmalloc + copy_from_user with vmemdup_user

Replace vmalloc() followed by copy_from_user() with vmemdup_user() to
improve nilfs_ioctl_clean_segments() and nilfs_ioctl_set_suinfo().  Use
kvfree() to free the buffers created by vmemdup_user().

Use u64_to_user_ptr() instead of manually casting the pointers and
remove the obsolete 'out_free' label.

No functional changes intended.

Link: https://lkml.kernel.org/r/20251030154700.7444-1-konishi.ryusuke@gmail.com
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>