VMCI: Fix process-to-process DRGAMs.

When sending between processes, we always schedule a work item.  Our work info
struct has the message embedded in the middle, which means that we end up
overwriting subsequent fields when we copy the (variable-length) message into
it.  Move it to the end of the struct.
Acked-by: NDmitry Torokhov <dtor@vmware.com>
Signed-off-by: NAndy King <acking@vmware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/vmw_vmci/vmci_datagram.c

@@ -42,9 +42,11 @@ struct datagram_entry {
 
 struct delayed_datagram_info {
 	struct datagram_entry *entry;
-	struct vmci_datagram msg;
 	struct work_struct work;
 	bool in_dg_host_queue;
+	/* msg and msg_payload must be together. */
+	struct vmci_datagram msg;
+	u8 msg_payload[];
 };
 
 /* Number of in-flight host->host datagrams */