fs/dirty_pages: fix inode reference count leakage error in dump_dirtypages_sb()

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8JUUC?from=project-issue



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Inode reference count leakage exists in dump_dirtypages_sb() function.
Executing iput(inode) in advance to avoid this problem.

Fixes: aeb96447 ("fs/dirty_pages: dump the number of dirty pages for each inode")
Signed-off-by: Zizhi Wo <wozizhi@huawei.com>