qeth: omit upstream checksumming for HiperSockets

For HiperSocket devices receive-path checksumming is not required.
Thus NO_CHECKSUMMING is used as default for HiperSocket interfaces.
For layer3 devices configured with NO_CHECKSUMMING received skbs
should have set their ip_summed field to CHECKSUM_UNNECESSARY.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>