Merge branch 'mvpp2-improvements-in-rx-path'

Matteo Croce says:

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mvpp2 improvements in rx path

Refactor some code in the RX path to allow prefetching some data from the
packet header. The first patch is only a refactor, the second one
reduces the data synced, while the third one adds the prefetch.

The packet rate improvement with the second patch is very small (1606 => 1620 kpps),
while the prefetch bumps it up by 14%: 1620 => 1853 kpps.
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Signed-off-by: David S. Miller <davem@davemloft.net>