Add an example SPI slave handler to allow remote control of system
reboot, power off, halt, and suspend.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: NMark Brown <broonie@kernel.org>