qeth: Use blkt defaults for OSA Express 4

The previous blkt defaults for OSA Express 4 cards produced inadequate
performance for streaming workloads. The present patch will apply a
set of more appropriate defaults.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Reviewed-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>