ANDROID: fscrypt: restore compatibility with old Android HW-wrapped keys

The upstream HW-wrapped key support in fscrypt is not fully UAPI and
on-disk compatible with the original Android solution, as the upstream
solution fixed several issues with the original Android solution.  The
divergence is fairly small, though.  Since UAPI and on-disk
compatibility with the original Android solution is still needed for
now, restore support for it using a fairly small compatibility patch.

Bug: 160883801
Change-Id: I3774bcfe0f8c3143e90b5187400a467afbb196eb
Signed-off-by: Eric Biggers <ebiggers@google.com>