xen/arm: pci: introduce PCI_PASSTHROUGH Kconfig option

Setting CONFIG_PCI_PASSTHROUGH=y will enable PCI passthrough on ARM,
even though the feature is not yet complete in the current upstream
codebase. The purpose of this is to make it easier to enable the
necessary configs (HAS_PCI, HAS_VPCI) for testing and development of PCI
passthrough on ARM, and to build it in CI.

Since PCI passthrough on ARM is still work in progress at this time,
make it depend on EXPERT.

Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/arm/Kconfig

@@ -8,6 +8,8 @@ config ARM_64
 	depends on !ARM_32
 	select 64BIT
 	select HAS_FAST_MULTIPLY
+	select HAS_VPCI_GUEST_SUPPORT if PCI_PASSTHROUGH
+	select HAS_PASSTHROUGH if PCI_PASSTHROUGH
 
 config ARM
 	def_bool y
@@ -258,6 +260,12 @@ config PARTIAL_EMULATION
 
 source "arch/arm/firmware/Kconfig"
 
+config PCI_PASSTHROUGH
+	bool "PCI passthrough" if EXPERT
+	depends on ARM_64
+	help
+	  This option enables PCI device passthrough
+
 endmenu
 
 menu "ARM errata workaround via the alternative framework"

xen/drivers/Kconfig

@@ -14,6 +14,7 @@ source "drivers/video/Kconfig"
 
 config HAS_VPCI
 	bool
+	select HAS_PCI
 
 config HAS_VPCI_GUEST_SUPPORT
 	bool