[S390] qdio: fix EQBS handling on CCQ96

QDIO returned from EQBS instruction in any case after return code
CCQ=96 was issued regardless whether buffer states for at least one
buffer were extracted or not.
This caused FCP devices to hang when running under z/VM and having
QIOASSASIST=ON and having high I/O rates.
In order to fix this qdio return code processing of EQBS instruction
after CCQ=96 is changed that buffers are returned and if no buffers
where extracted the instruction is repeated at once.

Signed-off-by: Klaus D. Wacker <kdwacker@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

drivers/s390/cio/qdio.c

@@ -195,6 +195,8 @@ qdio_do_eqbs(struct qdio_q *q, unsigned char *state,
 again:
 	ccq = do_eqbs(irq->sch_token, state, q_no, start, cnt);
 	rc = qdio_check_ccq(q, ccq);
+	if ((ccq == 96) && (tmp_cnt != *cnt))
+		rc = 0;
 	if (rc == 1) {
 		QDIO_DBF_TEXT5(1,trace,"eqAGAIN");
 		goto again;