Complate SD optration rt_err_t rt_sdcard_control()

Complate SD optration "rt_err_t rt_sdcard_control()"  at RT_DEVICE_CTRL_BLK_GETGEOME for GETGEOME.
else Initialization  was failed.
完善函数"rt_err_t rt_sdcard_control()"，当调用RT_DEVICE_CTRL_BLK_GETGEOME时，如果args返回空，会初始化失败。