irqchip/gic-v3-its: Remove artificial dependency on PCI

The GICv3 ITS doesn't really depend on PCI. Only the PCI/MSI
part of it does, and there is no reason not to blow away most
of the irqchip stack because PCI is not selected (though not
selecting PCI seem to be asking for punishment, but hey...).

So let's split the PCI-specific part from the ITS in the Kconfig
file, and let's make that part depend on PCI. Architecture specific
hacks (arch/arm{,64}/Kconfig) will be addressed in a separate patch.
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/Kconfig

@@ -41,8 +41,15 @@ config ARM_GIC_V3
 
 config ARM_GIC_V3_ITS
 	bool
+	select GENERIC_MSI_IRQ_DOMAIN
+	default ARM_GIC_V3
+
+config ARM_GIC_V3_ITS_PCI
+	bool
+	depends on ARM_GIC_V3_ITS
 	depends on PCI
 	depends on PCI_MSI
+	default ARM_GIC_V3_ITS
 
 config ARM_NVIC
 	bool

drivers/irqchip/Makefile

@@ -28,7 +28,8 @@ obj-$(CONFIG_ARM_GIC_PM)		+= irq-gic-pm.o
 obj-$(CONFIG_ARCH_REALVIEW)		+= irq-gic-realview.o
 obj-$(CONFIG_ARM_GIC_V2M)		+= irq-gic-v2m.o
 obj-$(CONFIG_ARM_GIC_V3)		+= irq-gic-v3.o irq-gic-common.o
-obj-$(CONFIG_ARM_GIC_V3_ITS)		+= irq-gic-v3-its.o irq-gic-v3-its-pci-msi.o irq-gic-v3-its-platform-msi.o irq-gic-v4.o
+obj-$(CONFIG_ARM_GIC_V3_ITS)		+= irq-gic-v3-its.o irq-gic-v3-its-platform-msi.o irq-gic-v4.o
+obj-$(CONFIG_ARM_GIC_V3_ITS_PCI)	+= irq-gic-v3-its-pci-msi.o
 obj-$(CONFIG_PARTITION_PERCPU)		+= irq-partition-percpu.o
 obj-$(CONFIG_HISILICON_IRQ_MBIGEN)	+= irq-mbigen.o
 obj-$(CONFIG_ARM_NVIC)			+= irq-nvic.o