[S390] Avoid sparse warnings.

Monthly sparse warning avoidance patch. Sigh.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 403957a..bfeca57 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2174,9 +2174,10 @@
 	return ret;
 }
 
-struct dasd_ccw_req * dasd_generic_build_rdc(struct dasd_device *device,
-					     void *rdc_buffer,
-					     int rdc_buffer_size, char *magic)
+static struct dasd_ccw_req *dasd_generic_build_rdc(struct dasd_device *device,
+						   void *rdc_buffer,
+						   int rdc_buffer_size,
+						   char *magic)
 {
 	struct dasd_ccw_req *cqr;
 	struct ccw1 *ccw;