driver core: auxiliary bus: add device creation helpers

Add helper functions to create a device on the auxiliary bus.

This is meant for fairly simple usage of the auxiliary bus, to avoid having
the same code repeated in the different drivers.

Suggested-by: Stephen Boyd <sboyd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20250218-aux-device-create-helper-v4-1-c3d7dfdea2e6@baylibre.com


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