docs/zh_CN: Update the translation of ksm to 6.0-rc7

Update to commit bc6a2828a963 ("ksm: add the ksm prefix
to the names of the ksm private structures")

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/60017007349357dc1fd8fa849a5ddb5672f8ab5b.1664360331.git.siyanteng@loongson.cn
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: rename Documentation/vm to Documentation/mm

so it will be consistent with code mm directory and with
Documentation/admin-guide/mm and won't be confused with virtual machines.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Acked-by: Wu XiangCheng <bobwxc@email.cn>