crypto: ccp - Introduce new API interface to indicate SEV-SNP Ciphertext hiding feature

Implement an API that checks the overall feature support for SEV-SNP
ciphertext hiding.

This API verifies both the support of the SEV firmware for the feature
and its enablement in the platform's BIOS.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>