arm64: Add architectural support for PCI

Use the generic PCI domain and OF functions to provide support for PCI
on arm64.

[bhelgaas: Change comments to use generic PCI, not just PCIe.  Nothing at
this level is PCIe-specific.]
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

diff --cc arch/arm64/Kconfig
Simple merge

diff --cc arch/arm64/include/asm/Kbuild
Simple merge

diff --cc arch/arm64/include/asm/io.h
Simple merge

diff --cc arch/arm64/include/asm/pci.h
Simple merge

diff --cc arch/arm64/include/asm/pgtable.h
Simple merge

diff --cc arch/arm64/kernel/Makefile
Simple merge

diff --cc arch/arm64/kernel/pci.c
Simple merge