Add option to read ROM layout from IFD

Add an option --ifd to read the ROM layout from an Intel Firmware
Descriptor (IFD). Works the same as the -l option, if given, -i
specifies the images to update.

v2: o Rebased on libflashrom, use libflashrom interface.
    o Use functions from ich_descriptors.c.

v3: o Move ich_descriptors.o to LIB_OBJS, thus build it independent
      of arch and programmers.
    o Bail out if we aren't compiled for little endian.
    o Update flashrom.8.tmpl.

v4: o Incorporated David's comments.
    o Removed single-character `-d` option.

v5: Changed region names to match the output of `ifdtool --layout ...`

Change-Id: Ifafff2bf6d5c5e62283416b3269723f81fdc0fa3
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/17953
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

layout.h

@@ -57,6 +57,13 @@ struct single_layout {
 	struct romentry entry;
 };
 
-const struct flashrom_layout *get_global_layout(void);
+struct ich_layout {
+	struct flashrom_layout base;
+	struct romentry entries[5];
+};
+
+struct flashrom_layout *get_global_layout(void);
+
+int process_include_args(struct flashrom_layout *);
 
 #endif				/* !__LAYOUT_H__ */