qeth: use default napi weight

Since commit 82dc3c63
"net: introduce NAPI_POLL_WEIGHT" network drivers receive a warning
when they use napi weight higher than NAPI_POLL_WEIGHT. This patch
reduces QETH_NAPI_WEIGHT from 128 to 64 (NAPI_POLL_WEIGHT).

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Frank Blaschka <blaschka@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>