ich_descriptors: Revise detection for chipsets w/ ICCRIBA

Detection based on ICCRIBA and FMSBA became a little messy lately.
However, there's a new static difference: Since 300 series (Cannon
Point), there is an MDTBA field in FLUMAP1 that has always been 0
(reserved) before. Taking this into account, we can relax the checks
on ICCRIBA.

Change-Id: I587ad1abe390843d4a9e74431b6fc4b63f8ba512
Signed-off-by: Nico Huber <nico.h@gmx.de>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/55647
Original-Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Original-Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/71399
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/ich_descriptors.h b/ich_descriptors.h
index 727a31b..274d0fe 100644
--- a/ich_descriptors.h
+++ b/ich_descriptors.h
@@ -521,7 +521,8 @@
 		struct {
 			uint32_t VTBA	:8,	/* ME VSCC Table Base Address */
 				 VTL	:8,	/* ME VSCC Table Length */
-					:16;
+					:8,
+				 MDTBA	:8;	/* MIP Descr. Table Base Addr. (new since Cannon Point/300) */
 		};
 	};
 	struct {