scsi: Document intentional fall through in scsi_req_length()

For clarity, and to hush up Coverity.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/scsi/scsi-bus.c

diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
index ae921a6..26770fb 100644
--- a/hw/scsi/scsi-bus.c
+++ b/hw/scsi/scsi-bus.c
@@ -938,6 +938,7 @@
         if (cmd->xfer == 0) {
             cmd->xfer = 256;
         }
+        /* fall through */
     case WRITE_10:
     case WRITE_VERIFY_10:
     case WRITE_12:
@@ -952,6 +953,7 @@
         if (cmd->xfer == 0) {
             cmd->xfer = 256;
         }
+        /* fall through */
     case READ_10:
     case RECOVER_BUFFERED_DATA:
     case READ_12: