ion: don't use id 0 for handle cookie

ion userspace clients think that the cookie is a pointer, so they
use NULL to check if the handle has been initialized.  Set the first
id number to 1.

Signed-off-by: Colin Cross <ccross@android.com>
Change-Id: Ifb9af6029a8b08f57e41bc6160cc11e11001a2a9