PCI/MSI: Only use the generic MSI layer when domain is hierarchical

Since d8a1cb75 ("PCI/MSI: Let pci_msi_get_domain use struct
device::msi_domain"), we use the MSI domain associated with the PCI device.

But finding an MSI domain doesn't mean that the domain is implemented using
the generic MSI domain API, and a number of MSI controllers are still using
arch_setup_msi_irq() and arch_teardown_msi_irqs().

Check that the domain we just obtained is hierarchical.  If it is, we can
use the new generic MSI stuff.  Otherwise we have to fall back to the old
arch_setup_msi_irq() and arch_teardown_msi_irqs() interfaces.

This avoids an oops in msi_domain_alloc_irqs() on systems with R-Car,
Tegra, Armada 370, and probably other DesignWare-based host controllers.

Fixes: d8a1cb75 ("PCI/MSI: Let pci_msi_get_domain use struct device::msi_domain")
Reported-by: Phil Edworthy <phil.edworthy@renesas.com>
Tested-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
CC: stable@vger.kernel.org	# v4.3+