Add support for building flashrom against libpayload

This doesn't include changes to the frontend which must be
done separately, so this won't work out of the box.
This code was tested on hardware.

Corresponding to flashrom svn r1184.

Signed-off-by: Patrick Georgi <patrick.georgi@coresystems.de>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

layout.c

@@ -134,6 +134,7 @@ int show_id(uint8_t *bios, int size, int force)
 }
 #endif
 
+#ifndef __LIBPAYLOAD__
 int read_romlayout(char *name)
 {
 	FILE *romlayout;
@@ -181,6 +182,7 @@ int read_romlayout(char *name)
 
 	return 0;
 }
+#endif
 
 int find_romentry(char *name)
 {