Introduce an include directory for header files

Move all header files to the new `include` directory.
Adapt include directives and build systems to the new directory.

Change-Id: Iaddd6bbfa0624b166d422f665877f096983bf4cf
Signed-off-by: Felix Singer <felix.singer@secunet.com>
Signed-off-by: Thomas Heijligen <thomas.heijligen@secunet.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/58622
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>

platform/endian_big.c

@@ -15,7 +15,7 @@
  * GNU General Public License for more details.
  */
 
-#include "../platform.h"
+#include "platform.h"
 
 /* convert cpu native endian to little endian */
 ___return_swapped(cpu_to_le, 8)

platform/endian_little.c

@@ -15,7 +15,7 @@
  * GNU General Public License for more details.
  */
 
-#include "../platform.h"
+#include "platform.h"
 
 /* convert cpu native endian to little endian */
 ___return_same(cpu_to_le, 8)

platform/memaccess.c

@@ -15,7 +15,7 @@
  * GNU General Public License for more details.
  */
 
-#include "../platform.h"
+#include "platform.h"
 
 /*
  * macro to return endian aware read function

platform/pci.h

@@ -1,25 +0,0 @@
-/*
- * This is a wrapper for libpci.
- * ...
- */
-
-
-#ifndef __PLATFORM_PCI_H__
-#define __PLATFORM_PCI_H__
-
-/*
- * An old libpci version seems to use the variable name "index" which triggers
- * shadowing warnings on systems which have the index() function in a default
- * #include or as builtin.
- */
-#define index shadow_workaround_index
-
-#if defined (__NetBSD__)
-#include <pci.h>
-#else
-#include <pci/pci.h>
-#endif
-
-#undef index
-
-#endif /* __PLATFORM_PCI_H__ */