driver core: platform: use bus_type functions

This works towards the goal mentioned in 2006 in commit 594c8281


("[PATCH] Add bus_type probe, remove, shutdown methods.").

The functions are moved to where the other bus_type functions are
defined and renamed to match the already established naming scheme.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201119124611.2573057-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>