[SCSI] More buffer->request_buffer changes

Seem like quite a few splipped through the cracks.  Here's a patch to
update all references I could find:

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/drivers/scsi/mesh.c b/drivers/scsi/mesh.c
index c887177..5572981 100644
--- a/drivers/scsi/mesh.c
+++ b/drivers/scsi/mesh.c
@@ -1268,7 +1268,7 @@
 		if (cmd->use_sg > 0) {
 			int nseg;
 			total = 0;
-			scl = (struct scatterlist *) cmd->buffer;
+			scl = (struct scatterlist *) cmd->request_buffer;
 			off = ms->data_ptr;
 			nseg = pci_map_sg(ms->pdev, scl, cmd->use_sg,
 					  cmd->sc_data_direction);