crypto: ccp - Add new SEV/SNP platform shutdown API

Add new API interface to do SEV/SNP platform shutdown when KVM module
is unloaded.

Reviewed-by: Dionna Glaze <dionnaglaze@google.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>