Merge branch 'mvpp2-per-cpu-buffers'

Matteo Croce says:

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mvpp2: per-cpu buffers

This patchset workarounds an PP2 HW limitation which prevents to use
per-cpu rx buffers.
The first patch is just a refactor to prepare for the second one.
The second one allocates percpu buffers if the following conditions are met:
- CPU number is less or equal 4
- no port is using jumbo frames

If the following conditions are not met at load time, of jumbo frame is enabled
later on, the shared allocation is reverted.
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Signed-off-by: David S. Miller <davem@davemloft.net>