arm64: suspend: make hw_breakpoint_restore static

hw_breakpoint_restore is only used within suspend.c, so it can be
declared static.
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/suspend.c

@@ -41,7 +41,7 @@ void notrace __cpu_suspend_save(struct cpu_suspend_ctx *ptr,
  * time the notifier runs debug exceptions might have been enabled already,
  * with HW breakpoints registers content still in an unknown state.
  */
-void (*hw_breakpoint_restore)(void *);
+static void (*hw_breakpoint_restore)(void *);
 void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
 {
 	/* Prevent multiple restore hook initializations */