sh: sdk7786: Use register_platform_power_off()

Utilize new register_platform_power_off() API that allows to register
multiple power-off handlers and deprecates global pm_power_off callback.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

arch/sh/boards/mach-sdk7786/setup.c

@@ -9,6 +9,7 @@
 #include <linux/platform_device.h>
 #include <linux/io.h>
 #include <linux/regulator/fixed.h>
+#include <linux/reboot.h>
 #include <linux/regulator/machine.h>
 #include <linux/smsc911x.h>
 #include <linux/i2c.h>
@@ -249,7 +250,7 @@ static void __init sdk7786_setup(char **cmdline_p)
 	pr_info("\tPCB revision:\t%d\n", fpga_read_reg(PCBRR) & 0xf);
 
 	machine_ops.restart = sdk7786_restart;
-	pm_power_off = sdk7786_power_off;
+	register_platform_power_off(sdk7786_power_off);
 
 	register_smp_ops(&shx3_smp_ops);
 }