Only minor differences in the Firmware Descriptor, compared to their
predecessors.

We extend our check on the `ICCRIBA` field in the descriptor to dis-
tinguish it from older generation. Alas, the `freq_read` field was
repurposed, so we can't use it as sanity check any more.

Change-Id: I1c2d1e8916cecd756e7ac1f0ba221d7cc361ba02
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/34072


Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>