x86: move more x86-generic functions out of PC files

These are needed by microvm too, so move them outside of PC-specific files.
With this patch, microvm.c need not include pc.h anymore.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 12ff55f..7b8da62 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -53,6 +53,7 @@
 /* Supported chipsets: */
 #include "hw/southbridge/piix.h"
 #include "hw/acpi/pcihp.h"
+#include "hw/i386/fw_cfg.h"
 #include "hw/i386/ich9.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/pci-host/q35.h"