nilfs2: convert to use the new mount API

Convert nilfs2 to use the new mount API.

[sandeen@redhat.com: v2]
Link: https://lkml.kernel.org/r/33d078a7-9072-4d8e-a3a9-dec23d4191da@redhat.com
Link: https://lkml.kernel.org/r/20240425190526.10905-1-konishi.ryusuke@gmail.com
[konishi.ryusuke: fixed missing SB_RDONLY flag repair in nilfs_reconfigure]
Link: https://lkml.kernel.org/r/33d078a7-9072-4d8e-a3a9-dec23d4191da@redhat.com
Link: https://lkml.kernel.org/r/20240424182716.6024-1-konishi.ryusuke@gmail.com


Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>