remoteproc: Update max_notifyid as we allocate vrings

Vrings are now allocated as we parse the resource table, before we
boot the rproc or register any virtio devices, so it's safe to bump
max_notifyid as part of this process.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
(cherry picked from commit 48f18f89)