Merge branch 'xen-netback'

David Vrabel says:

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xen-netback: fix ethtool stats and memory leak

A couple of bug fixes for netback:
- make ethool stats to report the correct values.
- don't leak 1 MiB every time a VIF is destroyed.

Changes in v2:
- Split 2nd patch into leak fix and refactor patches
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Acked-by: Ian Campbell <[email protected]>
Signed-off-by: David S. Miller <[email protected]>