i2c/i2c-omap: add a const qualifier

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

	drivers/i2c/busses/i2c-omap.c: In function 'omap_i2c_probe':
	drivers/i2c/busses/i2c-omap.c:1025: warning: assignment discards qualifiers from pointer target type
Reviewed-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/i2c/busses/i2c-omap.c

@@ -944,7 +944,8 @@ omap_i2c_probe(struct platform_device *pdev)
 	struct omap_i2c_dev	*dev;
 	struct i2c_adapter	*adap;
 	struct resource		*mem, *irq, *ioarea;
-	struct omap_i2c_bus_platform_data *pdata = pdev->dev.platform_data;
+	const struct omap_i2c_bus_platform_data *pdata =
+		pdev->dev.platform_data;
 	struct device_node	*node = pdev->dev.of_node;
 	const struct of_device_id *match;
 	irq_handler_t isr;