vfio: platform: Do not pass return buffer to ACPI _RST method

The ACPI _RST method has no return value, there's no need to pass a return
buffer to acpi_evaluate_object().

Fixes: d30daa33

 ("vfio: platform: call _RST method when using ACPI")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20221018152825.891032-1-rafaelmendsr@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>