hwaccess: move x86 port I/O related code into own files

Allow port I/O related code to be compiled independent from memory
mapping functionality. This enables for a better selection of needed
hardware access types.

Change-Id: I372b4a409f036da766c42bc406b596bc41b0f75a
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/60110
Original-Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72265
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/gfxnvidia.c b/gfxnvidia.c
index 1bf656c..381f861 100644
--- a/gfxnvidia.c
+++ b/gfxnvidia.c
@@ -20,6 +20,7 @@
 #include "flash.h"
 #include "programmer.h"
 #include "hwaccess.h"
+#include "hwaccess_x86_io.h"
 #include "platform/pci.h"
 
 #define PCI_VENDOR_ID_NVIDIA	0x10de