dma: tegra: make tegra_dma.chip_data a pointer to const data

This prepares *of_device_id.data becoming const. Without this change
the following warning would occur:

	drivers/dma/tegra20-apb-dma.c: In function 'tegra_dma_probe':
	drivers/dma/tegra20-apb-dma.c:1210:9: warning: assignment discards 'const' qualifier from pointer target type [enabled by default]

[ukl: split Laxman's patch to prevent warnings in the middle of the
series. Original patch was sent with msgid
1346217447-19730-1-git-send-email-ldewangan@nvidia.com]
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Acked-by: Vinod Koul <vinod.koul@linux.intel.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/dma/tegra20-apb-dma.c

@@ -201,7 +201,7 @@ struct tegra_dma {
 	struct clk			*dma_clk;
 	spinlock_t			global_lock;
 	void __iomem			*base_addr;
-	struct tegra_dma_chip_data	*chip_data;
+	const struct tegra_dma_chip_data *chip_data;
 
 	/* Some register need to be cache before suspend */
 	u32				reg_gen;
@@ -1197,7 +1197,7 @@ static int __devinit tegra_dma_probe(struct platform_device *pdev)
 	struct tegra_dma *tdma;
 	int ret;
 	int i;
-	struct tegra_dma_chip_data *cdata = NULL;
+	const struct tegra_dma_chip_data *cdata = NULL;
 
 	if (pdev->dev.of_node) {
 		const struct of_device_id *match;