support for backlog

Change-Id: Id8f503234e7afaa284e6b97dc264eb3a2af145c7

arch/arm64/kernel/timer.c

@@ -111,6 +111,8 @@ static void timer_handler(void *priv)
 		/* set timer re-enable for periodic */
 		arch_timer_reg_write(ARCH_TIMER_REG_TVAL, clocks);
 		arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
+
+		do_backlog();
 	}
 }