qeth: do not limit number of gso segments

To reduce the need of skb_linearize() calls, gso_max_segs of qeth
net_devices had been limited according to the maximum number of qdio SBAL
elements. But a gso segment cannot be larger than the mtu-size, while an
SBAL element can contain up to 4096 bytes. The gso_max_segs limitation
limits the maximum packet size given to the qeth driver. Performance
measurements with tso-enabled qeth network interfaces and mtu-size 1500
showed, that the disadvantage of smaller packets is much more severe than
the advantage of fewer skb_linearize() calls.
This patch gets rid of the gso_max_segs limitations in the qeth driver.

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>