dm: core: Allow for not controlling the power-domain by DM framework

In some remoteproc cases, enabling the power domain of the core will
start running the core. In such cases image should be loaded before
enabling the power domain. But the current DM framework enables the
power-domain by default during probe. This is causing the remotecore
to start and crash as there is no valid image loaded.

In order to avoid this introduce a DM flag that doesn't allow for
enabling/disabling the power-domain by DM framework.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>