device: Move MSI related data into a struct

The only unconditional part of MSI data in struct device is the irqdomain
pointer. Everything else can be allocated on demand. Create a data
structure and move the irqdomain pointer into it. The other MSI specific
parts are going to be removed from struct device in later steps.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20211210221813.617178827@linutronix.de