crypto: testmgr - Allow hash test vectors longer than a page

As it stands we will each test hash vector both linearly and as
a scatter list if applicable.  This means that we cannot have
vectors longer than a page, even with scatter lists.

This patch fixes this by skipping test vectors with np != 0 when
testing linearly.

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