rpmsg: virtio_rpmsg_bus: fix nameservice address

Commit 2a48d732 ("rpmsg: rpmsg_send() operations takes rpmsg_endpoint")
only changed the nameservice address for virtio_rpmsg_announce_create() but
did not do the same change for virtio_rpmsg_announce_destroy().

Signed-off-by: Henri Roosen <henri.roosen@ginzinger.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>