dm verity: correcting logic used with corrupted_errs counter

Current logic on handling corrupted_errs countes is not considering
DM_VERITY_MAX_CORRUPTED_ERRS limit so correcting the logic.

Change-Id: Ide3f3e6b9d8bec8f02cbb5a72b7d0935bcd87826
Signed-off-by: Ravi Kumar Siddojigari <rsiddoji@codeaurora.org>