driver core: make subsys_dev_iter_init() static

No one outside of drivers/base/bus.c calls this function so make it
static and remove the exported symbol.

Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230109175810.2965448-3-gregkh@linuxfoundation.org


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