Add John Allen as a new CCP driver maintainer. Additionally, break out
the driver SEV support and create a new maintainer entry, with Brijesh
Singh and Tom Lendacky as maintainers.

Cc: John Allen <john.allen@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: John Allen <john.allen@amd.com>
Acked-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>