Fix amd-sev firmware file for amd-snp

Luigi Leonardirequested to merge
luigileonardi/edk2:c9s into c9s

Merge Request Required Information

Summary of Changes

This is to use memory for all amd-sev modes. It is necessary because amd-sev-snp does not support pflash.

Approved Development Ticket(s)

Jira: RHEL-72447

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