Merge branch 'dsa-doc-fixes'

Florian Fainelli says:

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Documentation: dsa: misc fixes

Here are some miscelaneous documentation fixes for DSA, I targeted "net"
because these are not functional code changes, but still documentation fixes
per-se.

Changes in v2:

- reword what the port_vlan_filtering is about based on feedback from Vivien and Ido
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Signed-off-by: David S. Miller <davem@davemloft.net>