Merge branch 'virtio_net-mergeable-XDP'

Jason Wang says:

====================
Fix several issues of virtio-net mergeable XDP

Please review the patches that tries to fix several issues of
virtio-net mergeable XDP.

Changes from V1:
- check against 1 before decreasing instead of resetting to 1
- typoe fixes
====================

Signed-off-by: David S. Miller <davem@davemloft.net>