crypto: qat - remove empty functions and turn qat_uregister fn to void

Some code cleanups after crypto API changes:
- Change qat_algs_unregister to a void function to keep it consistent
  with qat_asym_algs_unregister.
- Remove empty functions qat_algs_init & qat_algs_exit.

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