nilfs2: add kernel-doc comments to nilfs_btree_convert_and_insert()

This commit adds kernel-doc style comments with complete parameter
descriptions for the function nilfs_btree_convert_and_insert.

Link: https://lkml.kernel.org/r/20240410075629.3441-3-konishi.ryusuke@gmail.com


Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>