PCI: Introduce new MSI chip infrastructure

The new struct msi_chip is used to associated an MSI controller with a
PCI bus. It is automatically handed down from the root to its children
during bus enumeration.

This patch provides default (weak) implementations for the architecture-
specific MSI functions (arch_setup_msi_irq(), arch_teardown_msi_irq()
and arch_msi_check_device()) which check if a PCI device's bus has an
attached MSI chip and forward the call appropriately.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Daniel Price <daniel.price@gmail.com>
Tested-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 46ada5c..b8eaa81 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -666,6 +666,7 @@
 
 	child->parent = parent;
 	child->ops = parent->ops;
+	child->msi = parent->msi;
 	child->sysdata = parent->sysdata;
 	child->bus_flags = parent->bus_flags;