crypto: qce - support zero length test vectors

crypto test module passes zero length vectors as test input to sha-1 and
sha-256. To provide correct output for these vectors, hash zero support
has been added as in other crypto drivers.

Signed-off-by: Sivaprakash Murugesan <sivaprak@codeaurora.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>