Properly set the length of the transfer so FastFat won't assert on us

reactos/drivers/storage/floppy

diff -u -r1.2 -r1.3
--- readwrite.c	10 Mar 2004 19:35:04 -0000	1.2
+++ readwrite.c	10 Mar 2004 20:17:26 -0000	1.3
@@ -708,6 +708,7 @@

   /* That's all folks! */
   KdPrint(("floppy: ReadWritePassive(): success; Completing with STATUS_SUCCESS\n"));
   Irp->IoStatus.Status = STATUS_SUCCESS;

+  Irp->IoStatus.Information = Length;

   IoCompleteRequest(Irp, IO_NO_INCREMENT);
   StopMotor(DriveInfo->ControllerInfo);
 }