[SCSI] fix up request buffer reference in various scsi drivers

Various scsi drivers use scsi_cmnd.buffer and scsi_cmnd.bufflen in their
queuecommand functions.  Those fields are internal storage for the
midlayer only and are used to restore the original payload after
request_buffer and request_bufflen have been overwritten for EH.  Using
the buffer and bufflen fields means they do very broken things in error
handling.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/gdth.c b/drivers/scsi/gdth.c
index d5740bb..9b918fd 100644
--- a/drivers/scsi/gdth.c
+++ b/drivers/scsi/gdth.c
@@ -2542,7 +2542,7 @@
     gdth_ha_str *ha;
     char *address;
 
-    cpcount = count<=(ushort)scp->bufflen ? count:(ushort)scp->bufflen;
+    cpcount = count<=(ushort)scp->request_bufflen ? count:(ushort)scp->request_bufflen;
     ha = HADATA(gdth_ctr_tab[hanum]);
 
     if (scp->use_sg) {