s390: clean up qdio.h

Fix two typos, document missing fields in the driver initialization
data and remove the copy&pasted 'pfmt' field from the qdr struct.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>