verity: remove special-case logic for the root node

Now that the root-node is the same width as the interior nodes
of the hash tree, we no longer need to make it a special case.

BUG=chromium-os:9752
TEST=Ran dm-verity.git unit tests. Ran platform_DMVerityCorruption on H/W.

kernel-next.git Review URL: http://codereview.chromium.org/6896044

TBRing. Alreadying LGTMed and committed to kernel-next.git.

Change-Id: I0edde02cb4b62b1121791badaf480ab46c2b44be

R=wad@chromium.org,taysom@chromium.org

Review URL: http://codereview.chromium.org/6880209
2 files changed