mmc: atmel-mci: Check pdata for NULL before dereferencing it at DMA config

Using an at91sam9g20ek development board with DTS configuration may trigger
a kernel panic because of a NULL pointer dereference exception, while
configuring DMA. Let's fix this by adding a check for pdata before
dereferencing it.
Signed-off-by: NBrent Taylor <motobud@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/atmel-mci.c

@@ -2438,7 +2438,7 @@ static int atmci_configure_dma(struct atmel_mci *host)
 		struct mci_platform_data *pdata = host->pdev->dev.platform_data;
 		dma_cap_mask_t mask;
 
-		if (!pdata->dma_filter)
+		if (!pdata || !pdata->dma_filter)
 			return -ENODEV;
 
 		dma_cap_zero(mask);