system: remove SYSTEM_BBRAM_IDX_VBNVBLOCK*
system: remove SYSTEM_BBRAM_IDX_VBNVBLOCK*

No current devices use VBNV in EC BBRAM... delete.

BUG=b:178689388
BRANCH=none
TEST=buildall

Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Change-Id: I181e69d9e61cc83b41a744c292b63b690e8007c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2668692
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec