Use qdio buffer helpers to manage the buffers used for the request
and response queues.

No functional change.
Reviewed-by: NSteffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>