nilfs2: convert sufile to use kmap_local

Concerning the code of the metadata file sufile for segment management,
convert all parts that uses the deprecated kmap_atomic() to use
kmap_local.  All transformations are directly possible here.

Link: https://lkml.kernel.org/r/20240122140202.6950-6-konishi.ryusuke@gmail.comSigned-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>