spi-topcliff-pch: Fix probing when DMA mode is used

If during registering SPI master due to SPI device probing a SPI transfer
is issued the DMA buffers are not allocated yet.

This fixes the following oops:
pch_spi 0000:02:0c.1: enabling device (0000 -> 0002)
pch_spi 0000:02:0c.1: master is unqueued, this is deprecated
BUG: unable to handle kernel NULL pointer dereference at   (null)
IP: [<c125aa05>] pch_spi_handle_dma+0x15c/0x6f4
[...]
Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-topcliff-pch.c

@@ -1452,6 +1452,11 @@ static int pch_spi_pd_probe(struct platform_device *plat_dev)
 
 	pch_spi_set_master_mode(master);
 
+	if (use_dma) {
+		dev_info(&plat_dev->dev, "Use DMA for data transfers\n");
+		pch_alloc_dma_buf(board_dat, data);
+	}
+
 	ret = spi_register_master(master);
 	if (ret != 0) {
 		dev_err(&plat_dev->dev,
@@ -1459,14 +1464,10 @@ static int pch_spi_pd_probe(struct platform_device *plat_dev)
 		goto err_spi_register_master;
 	}
 
-	if (use_dma) {
-		dev_info(&plat_dev->dev, "Use DMA for data transfers\n");
-		pch_alloc_dma_buf(board_dat, data);
-	}
-
 	return 0;
 
 err_spi_register_master:
+	pch_free_dma_buf(board_dat, data);
 	free_irq(board_dat->pdev->irq, data);
 err_request_irq:
 	pch_spi_free_resources(board_dat, data);