qeth: rework TSO functions

The maximum TSO size OSA can handle is 15 * PAGE_SIZE. This
patch reduces gso_max_size to this value and adds some sanity
checks and statistics to the TSO implementation.
Since only layer 3 is able to do TSO move all TSO related functions
to the qeth_l3 module.

Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/s390/net/qeth_l3.h b/drivers/s390/net/qeth_l3.h
index 9f143c8..ffa6fe4 100644
--- a/drivers/s390/net/qeth_l3.h
+++ b/drivers/s390/net/qeth_l3.h
@@ -60,5 +60,6 @@
 int qeth_l3_add_rxip(struct qeth_card *, enum qeth_prot_versions, const u8 *);
 void qeth_l3_del_rxip(struct qeth_card *card, enum qeth_prot_versions,
 			const u8 *);
+int qeth_l3_set_large_send(struct qeth_card *, enum qeth_large_send_types);
 
 #endif /* __QETH_L3_H__ */