[S390] s390mach compile warning

Fix the following compile warning:

drivers/s390/s390mach.c: In function 's390_collect_crw_info':
drivers/s390/s390mach.c:77: warning: ignoring return value of 'down_interruptibl
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/s390mach.c

@@ -48,10 +48,11 @@ s390_collect_crw_info(void *param)
 	int ccode;
 	struct semaphore *sem;
 	unsigned int chain;
+	int ignore;
 
 	sem = (struct semaphore *)param;
 repeat:
-	down_interruptible(sem);
+	ignore = down_interruptible(sem);
 	chain = 0;
 	while (1) {
 		if (unlikely(chain > 1)) {