xen/arm,arm64: update xen_restart after ff70130 and 7b6d864

Commit 7b6d864 (reboot: arm: change reboot_mode to use enum
reboot_mode) and ff70130 (arm64: use common reboot infrastructure)
change the prototype of arm_pm_restart on arm and arm64.
Update xen_restart accordingly.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

arch/arm/xen/enlighten.c

@@ -172,7 +172,7 @@ static void __init xen_percpu_init(void *unused)
 	enable_percpu_irq(xen_events_irq, 0);
 }
 
-static void xen_restart(char str, const char *cmd)
+static void xen_restart(enum reboot_mode reboot_mode, const char *cmd)
 {
 	struct sched_shutdown r = { .reason = SHUTDOWN_reboot };
 	int rc;