[S390] qdio: FCP/SCSI write I/O stagnates on LPAR

If running on LPAR, qdio might overlook an incoming buffer in certain
scenarios. The patch makes sure that incoming buffers are detected
immediately in all situations.

Signed-off-by: Ursula Braun <braunu@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>