vboot: remove VbExRegionRead vestiges

API was originally removed in CL:852798.

BUG=b:124141368, chromium:968464
TEST=make clean && make runtests
BRANCH=none

Change-Id: I29c0b642dbac80b5c8c7eceaf108843467a90be4
Signed-off-by: Joel Kitching <kitching@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2108751
Tested-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
diff --git a/firmware/include/vboot_api.h b/firmware/include/vboot_api.h
index 9d4bacb..3f0e2ef 100644
--- a/firmware/include/vboot_api.h
+++ b/firmware/include/vboot_api.h
@@ -611,13 +611,6 @@
  */
 vb2_error_t VbExLegacy(enum VbAltFwIndex_t altfw_num);
 
-/* Regions for VbExRegionRead() */
-enum vb_firmware_region {
-	VB_REGION_GBB,	/* Google Binary Block - see gbbheader.h */
-
-	VB_REGION_COUNT,
-};
-
 /**
  * Return number of locales supported
  *