KVM: SVM: Use str_enabled_disabled() helper in sev_hardware_setup()

Remove hard-coded strings by using the str_enabled_disabled() helper
function.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Pavan Kumar Paluri <papaluri@amd.com>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Link: https://lore.kernel.org/r/20241227094450.674104-2-thorsten.blum@linux.dev


Signed-off-by: Sean Christopherson <seanjc@google.com>