In case of in-place encryption fscrypt_ctx was allocated but never
released. Since we don't need it for in-place encryption, we skip
allocating it.

Fixes: 1c7dcf69 ("fscrypt: Add in-place encryption mode")
Signed-off-by: NDavid Gstir <david@sigma-star.at>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>