hw/acpi/cpu_hotplug.c calls pci_address_space_io(). Include
"hw/pci/pci.h" which declares it.

This fixes (when modifying unrelated headers):

  hw/acpi/cpu_hotplug.c:103:28: error: implicit declaration of function 'pci_address_space_io' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
      MemoryRegion *parent = pci_address_space_io(PCI_DEVICE(gpe_cpu->device));
                             ^

Acked-by: John Snow <jsnow@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200228114649.12818-11-philmd@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>