Disable Rx checksum offload until I find more clue why it breaks under certain environments. However give users chance to override it when he/she surely knows his/her hardware works with Rx checksum offload.
Disable Rx checksum offload until I find more clue why it breaks
under certain environments. However give users chance to override
it when he/she surely knows his/her hardware works with Rx checksum
offload.

Reported by:	Ulrich Spoerlein ( uqs <> spoerlein dot net )
MFC after:	1 week
Approved by:	re (kensmith)

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