vboot: prepare for x86 verstage

In order to support x86 verstage proper the work buffer
needs to live in cache-as-ram. However, after cache-as-ram
is torn down one still needs the verification results to
know which slot was selected. Though the platforms with
a dedicated SRAM can just use the work buffer in SRAM, the
x86 cache-as-ram platforms need a place to stash the
results. For that situation cbmem is employed. This works
because when cbmem is initialized cache-as-ram is still
enabled. The VBOOT_DYNAMIC_WORK_BUFFER case assumes
verified boot doesn't start until after cbmem is up. That
doesn't change, but it's a goal to get rid of that option
entirely once all other x86 platforms are moved over to
pre-romstage vboot.

BUG=chrome-os-partner:44827
BRANCH=None
TEST=Built and booted glados with pre-romstage verification
     as well as VBOOT_DYNAMIC_WORK_BUFFER case.

Change-Id: I7eacd0edb2b6ca52b59b74075d17c00b50676d4c
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11821
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/commonlib/include/commonlib/cbmem_id.h

@@ -65,6 +65,7 @@
 #define CBMEM_ID_TCPA_LOG	0x54435041
 #define CBMEM_ID_TIMESTAMP	0x54494d45
 #define CBMEM_ID_VBOOT_HANDOFF	0x780074f0
+#define CBMEM_ID_VBOOT_SEL_REG	0x780074f1
 #define CBMEM_ID_VBOOT_WORKBUF	0x78007343
 #define CBMEM_ID_WIFI_CALIBRATION 0x57494649
 
@@ -108,6 +109,7 @@
 	{ CBMEM_ID_TCPA_LOG,		"TCPA LOG   " }, \
 	{ CBMEM_ID_TIMESTAMP,		"TIME STAMP " }, \
 	{ CBMEM_ID_VBOOT_HANDOFF,	"VBOOT      " }, \
+	{ CBMEM_ID_VBOOT_SEL_REG,	"VBOOT SEL  " }, \
 	{ CBMEM_ID_VBOOT_WORKBUF,	"VBOOT WORK " }, \
 	{ CBMEM_ID_WIFI_CALIBRATION,	"WIFI CLBR  " },
 #endif /* _CBMEM_ID_H_ */