PCI: hv: Set up MSI domain at bridge probing time

Since PCI_HYPERV depends on PCI_MSI_IRQ_DOMAIN which selects
GENERIC_MSI_IRQ_DOMAIN, we can use dev_set_msi_domain() to set up the
MSI domain at probing time, and this works for both x86 and ARM64.

Therefore use it as the preparation for ARM64 Hyper-V PCI support.

As a result, no longer need to maintain ->fwnode in x86 specific
pci_sysdata, and make hv_pcibus_device own it instead.

Link: https://lore.kernel.org/r/20210726180657.142727-8-boqun.feng@gmail.com


Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>