crypto: ccp: Provide an API to issue SEV and SNP commands

Export sev_do_cmd() as a generic API for the hypervisor to issue
commands to manage an SEV or an SNP guest. The commands for SEV and SNP
are defined in the SEV and SEV-SNP firmware specifications.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240126041126.1927228-15-michael.roth@amd.com