powerpc: Use do_kernel_power_off()

Kernel now supports chained power-off handlers. Use do_kernel_power_off()
that invokes chained power-off handlers. It also invokes legacy
pm_power_off() for now, which will be removed once all drivers will
be converted to the new sys-off API.
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

arch/powerpc/kernel/setup-common.c

@@ -161,9 +161,7 @@ void machine_restart(char *cmd)
 void machine_power_off(void)
 {
 	machine_shutdown();
-	if (pm_power_off)
-		pm_power_off();
-
+	do_kernel_power_off();
 	smp_send_stop();
 	machine_hang();
 }

arch/powerpc/xmon/xmon.c

@@ -1243,8 +1243,7 @@ static void bootcmds(void)
 	} else if (cmd == 'h') {
 		ppc_md.halt();
 	} else if (cmd == 'p') {
-		if (pm_power_off)
-			pm_power_off();
+		do_kernel_power_off();
 	}
 }