driver core: soc: remove layering violation for the soc_bus

The soc_bus code pokes around in the internal bus structures assuming
that it "knows" if a field is not set that it has not been registered
yet.  That isn't a safe assumption, so just remove the layering
violation entirely and keep track if the bus has been registered or not
ourselves.

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20230130171059.1784057-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>