Fix up previous patch that failed to properly fix mem leak in 
rfc4106_set_hash_subkey(). This add-on patch; fixes the leak. moves 
kfree() out of the error path, returns -ENOMEM rather than -EINVAL when 
ablkcipher_request_alloc() fails.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>