[patch 7/10] s390: qeth bug fixes.

From: Frank Pavlic <pavlic@de.ibm.com>

qeth network driver changes:
 - Removed redundant code, use the same qeth_fill_buffer_frag
   for TSO path either
 - Using skb->frags solely is not correct since skb->data still
   points to the beginning of the whole data, even when it is
   a small portion we have to fill the qdio buffer with it.
Signed-off-by: Frank Pavlic <pavlic@de.ibm.com>