mmc: renesas_sdhi: Add missing checks for the presence of quirks

When running on an system without any quirks (e.g. R-Car V3U), the
kernel crashes with a NULL pointer dereference:

    Unable to handle kernel NULL pointer dereference at virtual address 0000000000000002
    ...
    Hardware name: Renesas Falcon CPU and Breakout boards based on r8a779a0 (DT)
    Workqueue: events_freezable mmc_rescan
    ...
    Call trace:
     renesas_sdhi_internal_dmac_start_dma+0x54/0x12c
     tmio_process_mrq+0x124/0x274

Fix this by adding the missing checks for the validatity of the
priv->quirks pointer.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/cc3178c2ff60f640f4d5a071d51f6b0b1db37656.1648822020.git.geert+renesas@glider.beSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/renesas_sdhi_internal_dmac.c

@@ -372,7 +372,7 @@ renesas_sdhi_internal_dmac_start_dma(struct tmio_mmc_host *host,
 	struct scatterlist *sg = host->sg_ptr;
 	u32 dtran_mode = DTRAN_MODE_BUS_WIDTH;
 
-	if (!priv->quirks->fixed_addr_mode)
+	if (!(priv->quirks && priv->quirks->fixed_addr_mode))
 		dtran_mode |= DTRAN_MODE_ADDR_MODE;
 
 	if (!renesas_sdhi_internal_dmac_map(host, data, COOKIE_MAPPED))
@@ -380,7 +380,7 @@ renesas_sdhi_internal_dmac_start_dma(struct tmio_mmc_host *host,
 
 	if (data->flags & MMC_DATA_READ) {
 		dtran_mode |= DTRAN_MODE_CH_NUM_CH1;
-		if (priv->quirks->dma_one_rx_only &&
+		if (priv->quirks && priv->quirks->dma_one_rx_only &&
 		    test_and_set_bit(SDHI_INTERNAL_DMAC_RX_IN_USE, &global_flags))
 			goto force_pio_with_unmap;
 	} else {