KVM: SEV: Don't explicitly pass PSC buffer to snp_begin_psc()

KVM: SEV: Don't explicitly pass PSC buffer to snp_begin_psc()

Stop explicitly passing the PSC buffer to snp_begin_psc(): it *must*
be the scratch area.  This will allow fixing a variety of bugs without
further complicating the code.

No functional change intended.

Cc: stable@vger.kernel.org
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260501202250.2115252-9-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>