PCI/ACPI: Guard ARM64-specific mcfg_quirks

Guard ARM64-specific quirks with CONFIG_ARM64 to avoid build errors,
since mcfg_quirks will be shared by more than one architectures.

Link: https://lore.kernel.org/r/20220714124216.1489304-2-chenhuacai@loongson.cn


Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>