ANDROID: dm verity fec: initialize recursion level

Explicitly initialize recursion level to zero at the beginning of each
I/O operation.

Bug: 28943429
Change-Id: I00c612be2b8c22dd5afb65a739551df91cb324fc
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
(cherry picked from commit 32ffb3a22d7fd269b2961323478ece92c06a8334)
Git-commit: d053106b
Git-repo: https://android.googlesource.com/kernel/common


Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>