To avoid unnecessary pollution of the global symbol namespace move the
driver core exports into their own namespace and import that into the two
bus modules.

For more info see https://lwn.net/Articles/760045/Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Mike Looijmans <mike.looijmans@topic.nl>
Link: https://lore.kernel.org/r/20220116180535.2367780-11-jic23@kernel.org