Add verify trim support

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/ioengine.h b/ioengine.h
index 389e95a..f6238f8 100644
--- a/ioengine.h
+++ b/ioengine.h
@@ -9,6 +9,7 @@
 	IO_U_F_FREE_DEF		= 1 << 2,
 	IO_U_F_IN_CUR_DEPTH	= 1 << 3,
 	IO_U_F_BUSY_OK		= 1 << 4,
+	IO_U_F_TRIMMED		= 1 << 5,
 };
 
 /*