crypto: api - Add crypto_requires_off helper

This patch adds crypto_requires_off which is an extension of
crypto_requires_sync for similar bits such as NEED_FALLBACK.

Cc: stable@vger.kernel.org #4.10
Suggested-by: Marcelo Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>