[S390] dasd: fix endless loop in erp

If not enough memory is available to build a new erp request it ended
up in an endless loop trying to build erp requests. Fixed the loop to
proceed the next request instead.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index bbea90b..acf222f 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -1899,7 +1899,8 @@
 		/*  Process requests that may be recovered */
 		if (cqr->status == DASD_CQR_NEED_ERP) {
 			erp_fn = base->discipline->erp_action(cqr);
-			erp_fn(cqr);
+			if (IS_ERR(erp_fn(cqr)))
+				continue;
 			goto restart;
 		}