remoteproc: Move vdev handling to boot/shutdown

The newly introduced "always-on" flag allows us to stop giving the vdevs
special treatment. The ordering of resource allocation and life cycle of
the remote processor is kept intact.

This allows us to mark a remote processor with vdevs to not boot unless
explicitly requested to do so by a client driver.

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Loic Pallardy <loic.pallardy@st.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>