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>

include/platform/pci.h

@@ -0,0 +1,25 @@
+/*
+ * 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__ */