netdevsim: make nsim_bus const

Now that the driver core can properly handle constant struct bus_type,
move the nsim_bus 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>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/bus.c

@@ -260,7 +260,7 @@ static int nsim_num_vf(struct device *dev)
 	return nsim_bus_dev->num_vfs;
 }
 
-static struct bus_type nsim_bus = {
+static const struct bus_type nsim_bus = {
 	.name		= DRV_NAME,
 	.dev_name	= DRV_NAME,
 	.bus_groups	= nsim_bus_groups,