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: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Andy King <acking@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>