locomo: make locomo_bus_type constant and static

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

It's also never used outside of arch/arm/common/locomo.c so make it
static and don't export it as no one is using it.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc:  <linux-arm-kernel@lists.infradead.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/2023121905-idiom-opossum-1ba3@gregkh


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