peci: Make peci_bus_type const

peci: Make peci_bus_type const

Now that the driver core can properly handle constant struct bus_type,
move the peci_bus_type variable to be a constant structure as well,
placing it into read-only memory which can not be modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240210-bus_cleanup-peci-v1-1-1e64bef6efc0@marliere.net
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>