ssi: Add slave autoconnect helper Added helper function to automatically connect SPI slaves based on the QOM child nodes of a device. A SSI master device can call this routine to automatically hook-up all child nodes to its SPI bus. Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com> Acked-by: Peter Maydell <peter.maydell@linaro.org>