This prepares *of_device_id.data becoming const. Without this change
the following warning would occur:
	drivers/spi/spi-omap2-mcspi.c: In function 'omap2_mcspi_probe':
	drivers/spi/spi-omap2-mcspi.c:1118: warning: assignment discards qualifiers from pointer target type
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
 static int __devinit omap2_mcspi_probe(struct platform_device *pdev)
 {
        struct spi_master       *master;
-       struct omap2_mcspi_platform_config *pdata;
+       const struct omap2_mcspi_platform_config *pdata;
        struct omap2_mcspi      *mcspi;
        struct resource         *r;
        int                     status = 0, i;