修正qemu-vexpress-a9系统心跳不准的问题

bsp/qemu-vexpress-a9/drivers/drv_timer.c

@@ -73,7 +73,7 @@ int rt_hw_timer_init(void)
     val |= (TIMER_CTRL_32BIT | TIMER_CTRL_PERIODIC | TIMER_CTRL_IE);
     TIMER_CTRL(TIMER_HW_BASE) = val;
 
-    TIMER_LOAD(TIMER_HW_BASE) = 1000;
+    TIMER_LOAD(TIMER_HW_BASE) = 1000000/RT_TICK_PER_SECOND;
 
     /* enable timer */
     TIMER_CTRL(TIMER_HW_BASE) |= TIMER_CTRL_ENABLE;