ANDROID: dm verity fec: add missing release from fec_ktype

Add a release function to allow destroying the dm-verity device.

Bug: 27928374
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Change-Id: Ic0f7c17e4889c5580d70b52d9a709a37165a5747
(cherry picked from commit 0039ccf47c8f99888f7b71b2a36a68a027fbe357)
Git-commit: c4d8e3e8
Git-repo: https://android.googlesource.com/kernel/common


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