crypto: qat - refactor FW signing algorithm

crypto: qat - refactor FW signing algorithm

The current implementation is designed to support single FW signing
authentication only.
Refactor the implementation to support other FW signing methods.

This does not include any functional change.

Co-developed-by: Suman Kumar Chakraborty <suman.kumar.chakraborty@intel.com>
Signed-off-by: Suman Kumar Chakraborty <suman.kumar.chakraborty@intel.com>
Signed-off-by: Jack Xu <jack.xu@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>