ARM: restart: add restart hook to machine_desc record

Add a restart hook to the machine_desc record so we don't have to
populate all platforms with init_early methods to initialize the
arm_pm_restart function pointer.

Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 7e7977a..4755e28 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -922,6 +922,9 @@
 	paging_init(mdesc);
 	request_standard_resources(mdesc);
 
+	if (mdesc->restart)
+		arm_pm_restart = mdesc->restart;
+
 	unflatten_device_tree();
 
 #ifdef CONFIG_SMP