mmc: via-sdmmc: Fix data race bug

via_save_pcictrlreg() should be called with host->lock held
as it writes to pm_pcictrl_reg, otherwise there can be a race
condition between via_sd_suspend() and via_sdc_card_detect().
The same pattern is used in the function via_reset_pcictrl()
as well, where via_save_pcictrlreg() is called with host->lock
held.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: NMadhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Link: https://lore.kernel.org/r/20200822061528.7035-1-madhuparnabhowmik10@gmail.comSigned-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/via-sdmmc.c

@@ -1257,11 +1257,14 @@ static void __maybe_unused via_init_sdc_pm(struct via_crdr_mmc_host *host)
 static int __maybe_unused via_sd_suspend(struct device *dev)
 {
 	struct via_crdr_mmc_host *host;
+	unsigned long flags;
 
 	host = dev_get_drvdata(dev);
 
+	spin_lock_irqsave(&host->lock, flags);
 	via_save_pcictrlreg(host);
 	via_save_sdcreg(host);
+	spin_unlock_irqrestore(&host->lock, flags);
 
 	device_wakeup_enable(dev);