driver core: bus: clean up driver_find()

Convert the driver_find() function to use bus_to_subsys() and not use
the back-pointer to the private structure.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230208111330.439504-16-gregkh@linuxfoundation.org


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