KVM: x86: Select KVM_GENERIC_PRIVATE_MEM directly from KVM_SW_PROTECTED_VM

KVM: x86: Select KVM_GENERIC_PRIVATE_MEM directly from KVM_SW_PROTECTED_VM

Now that KVM_SW_PROTECTED_VM doesn't have a hidden dependency on KVM_X86,
select KVM_GENERIC_PRIVATE_MEM from within KVM_SW_PROTECTED_VM instead of
conditionally selecting it from KVM_X86.

No functional change intended.

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Message-ID: <20250729225455.670324-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>