Merge branch 'dsa-fast-ageing'

Vladimir Oltean says:

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DSA fast ageing fixes/improvements

These are 2 small improvements brought to the DSA fast ageing changes
merged earlier today.

Patch 1 restores the behavior for DSA drivers that don't implement the
.port_bridge_flags function (I don't think there is any breakage due
to the new behavior, but just to be sure). This came as a result of
Andrew's review.

Patch 2 reduces the number of fast ages of a port from 2 to 1 when it
leaves a bridge.
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Signed-off-by: David S. Miller <davem@davemloft.net>