crypto: testmgr - Add a test case for import()/export()

Modify __test_hash() so that hash import/export can be tested
from within the kernel. The test is unconditionally done when
a struct hash_testvec has its .np > 1.

v3: make the test unconditional
v2: Leverage template[i].np as suggested by Tim Chen

Signed-off-by: Rui Wang <rui.y.wang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>