mmc: sdhci-msm: Override DLL_CONFIG only if the valid value is supplied

During DLL initialization, the DLL_CONFIG register value would be
updated with the value supplied from the device-tree.

Override this register only if a valid value is supplied.

Fixes: 03591160 ("mmc: sdhci-msm: Read and use DLL Config property from device tree file")
Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
Link: https://lore.kernel.org/r/1594213888-2780-1-git-send-email-vbadigan@codeaurora.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-msm.c

@@ -618,8 +618,9 @@ static int msm_init_cm_dll(struct sdhci_host *host)
 	config &= ~CORE_CLK_PWRSAVE;
 	writel_relaxed(config, host->ioaddr + msm_offset->core_vendor_spec);
 
-	config = msm_host->dll_config;
-	writel_relaxed(config, host->ioaddr + msm_offset->core_dll_config);
+	if (msm_host->dll_config)
+		writel_relaxed(msm_host->dll_config,
+				host->ioaddr + msm_offset->core_dll_config);
 
 	if (msm_host->use_14lpp_dll_reset) {
 		config = readl_relaxed(host->ioaddr +