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>

libflashrom.h

@@ -63,6 +63,7 @@ int flashrom_image_write(struct flashrom_flashctx *, const void *buffer, size_t
 int flashrom_image_verify(struct flashrom_flashctx *, const void *buffer, size_t buffer_len);
 
 struct flashrom_layout;
+int flashrom_layout_read_from_ifd(struct flashrom_layout **, struct flashrom_flashctx *, const void *dump, size_t len);
 int flashrom_layout_include_region(struct flashrom_layout *, const char *name);
 void flashrom_layout_release(struct flashrom_layout *);
 void flashrom_layout_set(struct flashrom_flashctx *, const struct flashrom_layout *);