vboot: remove rogue vboot_struct.h include

As part of vboot1 deprecation, remove an unused vboot_struct.h
include.  coreboot is now free of vboot1 data structure use.
One vboot_api.h include remains as part of security/vboot/ec_sync.c.

BUG=b:124141368
TEST=make clean && make test-abuild
BRANCH=none

Change-Id: I042d692aa252f8f859d4005455eb6a2eabc24a87
Signed-off-by: Joel Kitching <kitching@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39024
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/vendorcode/google/chromeos/gnvs.c

@@ -22,7 +22,6 @@
 #include <fmap.h>
 #include <security/vboot/vbnv.h>
 #include <security/vboot/vboot_common.h>
-#include <vboot_struct.h>
 
 #include "chromeos.h"
 #include "gnvs.h"