PCI/MSI: Make pci_host_common_probe() declare its reliance on MSI domains

The generic PCI host driver relies on MSI domains for MSIs to
be provided to its end-points. Make this dependency explicit.

This cures the warnings occuring on arm/arm64 VMs when booted
with PCI virtio devices and no MSI controller (no GICv3 ITS,
for example).

It is likely that other drivers will need to express the same
dependency.

Link: https://lore.kernel.org/r/20210330151145.997953-12-maz@kernel.org


Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>