genirq/msi: Provide msi_device_populate/destroy_sysfs()

Add new allocation functions which can be activated by domain info
flags. They store the groups pointer in struct msi_device_data.

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>
Link: https://lore.kernel.org/r/20211210221813.988659194@linutronix.de