[bug report] ASoC: mediatek: implement mediatek common structure

[Dan Carpenter]

Hello Garlic Tseng,

The patch 283b612429a2: "ASoC: mediatek: implement mediatek common
structure" from Jun 17, 2016, leads to the following
Smatch static checker warning:

	sound/soc/mediatek/common/mtk-afe-fe-dai.c:364 mtk_afe_resume()
	error: we previously assumed 'afe->reg_back_up' could be null (see line 359)

sound/soc/mediatek/common/mtk-afe-fe-dai.c
    354         if (pm_runtime_status_suspended(dev) || !afe->suspended)
    355                 return 0;
    356 
    357         afe->runtime_resume(dev);
    358 
    359         if (!afe->reg_back_up)
    360                 dev_dbg(dev, "%s no reg_backup\n", __func__);

Should this return?  Also when ->reg_back_up is allocated there is no
check for NULL so it seems like a very possible condition.

    361 
    362         for (i = 0; i < afe->reg_back_up_list_num; i++)
    363                 mtk_regmap_write(regmap, afe->reg_back_up_list[i],
--> 364                                  afe->reg_back_up[i]);
    365 
    366         afe->suspended = false;
    367         return 0;
    368 }

regards,
dan carpenter