update dmi docs

[wbc6080]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  docs update

• What is the current behavior? (You can also link to an open issue here)
  update dmi docs

• What is the new behavior (if this is a feature change)?

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

• Other information:
  related to Umbrella Issue for KubeEdge Documentation Improvement #433

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[wbc6080]

We have summarized all the documents in the device part to #439
/close

[kubeedge-bot]

@wbc6080: Closed this PR.

In response to this:

We have summarized all the documents in the device part to #439
/close

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