scsi: stex: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning by
explicitly adding a break statement instead of letting the code fall
through to the next case.

Link: https://github.com/KSPP/linux/issues/115
Link: https://lore.kernel.org/r/20a7bcc10af2b762325c7078a4f472121a4fabc7.1605896060.git.gustavoars@kernel.orgSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/stex.c

@@ -685,6 +685,7 @@ stex_queuecommand_lck(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *))
 			done(cmd);
 			return 0;
 		}
+		break;
 	default:
 		break;
 	}