mfd: fix tmio related warnings

We can not have .driver_data as const since platform_set_drvdata() doesnt take
a const.
The hclk mmc_data field can be const though.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/include/linux/mfd/tmio.h b/include/linux/mfd/tmio.h
index c377118..6b9c5d0 100644
--- a/include/linux/mfd/tmio.h
+++ b/include/linux/mfd/tmio.h
@@ -22,7 +22,7 @@
  * data for the MMC controller
  */
 struct tmio_mmc_data {
-	unsigned int		hclk;
+	const unsigned int		hclk;
 };
 
 /*