amdfwtool: combo: Add combo feature for BIOS table

It is similar to PSP combo.

Change-Id: If0523a4a0e1f31969e4bbaa6062dcc0f2d6da420
Signed-off-by: Zheng Bao <fishbaozi@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66856
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>

util/amdfwtool/amdfwtool.h

@@ -317,6 +317,7 @@ typedef struct _ish_directory_table {
 #define PSP2_COOKIE 0x50535032		/* 'PSP2' */
 #define BHD_COOKIE 0x44484224		/* 'DHB$ */
 #define BHDL2_COOKIE 0x324c4224		/* '2LB$ */
+#define BHD2_COOKIE 0x44484232		/* 'DHB2' */
 
 #define PSP_LVL1 (1 << 0)
 #define PSP_LVL2 (1 << 1)