ANDROID: dm-default-key: Update key size for wrapped keys

Wrapped keys can have key sizes of variable length.
Pass in the wrapped key size sent from userspace instead
of using a fixed value from the cipher when calling into
blk-crypto.

Bug: 156230001

Test: Validated metadata encryption with wrappedkey_v0 when /data
      is mounted on a dm device.
      fstab: metadata_encryption=aes-256-xts:wrappedkey_v0

Change-Id: I0ad1f2ced57c6b2b34f6e55942eba2e1c2c030b1
Signed-off-by: Gaurav Kashyap <gaurkash@codeaurora.org>