arm64: vexpress: Add support for poweroff/restart

This patch adds the arm_pm_poweroff definition expected by the
vexpress-poweroff.c driver and enables the latter for arm64.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Pawel Moll <pawel.moll@arm.com>
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 116a60a..bbefb6f 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -81,8 +81,8 @@
 void (*pm_power_off)(void);
 EXPORT_SYMBOL_GPL(pm_power_off);
 
-void (*pm_restart)(const char *cmd);
-EXPORT_SYMBOL_GPL(pm_restart);
+void (*arm_pm_restart)(char str, const char *cmd);
+EXPORT_SYMBOL_GPL(arm_pm_restart);
 
 
 /*
@@ -164,8 +164,8 @@
 	local_fiq_disable();
 
 	/* Now call the architecture specific reboot code. */
-	if (pm_restart)
-		pm_restart(cmd);
+	if (arm_pm_restart)
+		arm_pm_restart('h', cmd);
 
 	/*
 	 * Whoops - the architecture was unable to reboot.