crypto: qat - Don't attempt to register algorithm multiple times

When multiple devices are present in the system the driver attempts
to register the same algorithm many times.

Changes in v2:
 - use proper synchronization mechanizm between register and unregister

Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>