crypto: ccp: Handle the legacy TMR allocation when SNP is enabled

The behavior and requirement for the SEV-legacy command is altered when
the SNP firmware is in the INIT state. See SEV-SNP firmware ABI
specification for more details.

Allocate the Trusted Memory Region (TMR) as a 2MB-sized/aligned region
when SNP is enabled to satisfy new requirements for SNP. Continue
allocating a 1MB-sized region for !SNP configuration.

  [ bp: Carve out TMR allocation into a helper. ]

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/20240126041126.1927228-17-michael.roth@amd.com