crypto: ccp: Define the SEV-SNP commands

AMD introduced the next generation of SEV called SEV-SNP (Secure Nested
Paging). SEV-SNP builds upon existing SEV and SEV-ES functionality while
adding new hardware security protection.

Define the commands and structures used to communicate with the AMD-SP
when creating and managing the SEV-SNP guests. The SEV-SNP firmware spec
is available at developer.amd.com/sev.

  [ mdr: update SNP command list and SNP status struct based on current
    spec, use C99 flexible arrays, fix kernel-doc issues. ]

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Ashish Kalra <ashish.kalra@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/20240126041126.1927228-13-michael.roth@amd.com