genirq/msi: Add bus token to struct msi_domain_info

Add a bus token member to struct msi_domain_info and let
msi_create_irq_domain() set the bus token.

That allows to remove the bus token updates at the call sites.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20221111122014.294554462@linutronix.de