[SCSI] Fix incorrect pointer in megaraid.c MODE_SENSE emulation

The SCSI megaraid drive goes to great effort to kmap
the scatterlist buffer (if used), but then uses the
wrong pointer when copying to it afterward.

Signed-off-by:  Mark Lord <lkml@rtr.ca>
Acked by: Ju, Seokmann <Seokmann.Ju@engenio.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/megaraid.c

@@ -664,7 +664,7 @@ mega_build_cmd(adapter_t *adapter, Scsi_Cmnd *cmd, int *busy)
 					sg->offset;
 			} else
 				buf = cmd->request_buffer;
-			memset(cmd->request_buffer, 0, cmd->cmnd[4]);
+			memset(buf, 0, cmd->cmnd[4]);
 			if (cmd->use_sg) {
 				struct scatterlist *sg;