ubifs: remove unnecessary #ifdef around fscrypt_ioctl_get_policy()

When !CONFIG_FS_ENCRYPTION, fscrypt_ioctl_get_policy() is already
stubbed out to return -EOPNOTSUPP, so the extra #ifdef is not needed.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>