x86/sev/docs: Document the SNP Reverse Map Table (RMP)

x86/sev/docs: Document the SNP Reverse Map Table (RMP)

Update the AMD memory encryption documentation to include information on
the Reverse Map Table (RMP) and the two table formats.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Link: https://lore.kernel.org/r/d3feea54912ad9ff2fc261223db691ca11fc547f.1733172653.git.thomas.lendacky@amd.com