Add the missing unlock before return from function sun4i_hash()
in the error handling case.

Fixes: 477d9b2e ("crypto: sun4i-ss - unify update/final function")
Signed-off-by: Wei Yongjun <weiyj.lk@gmail.com>
Acked-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>