mfd: remove driver_data direct access of struct device

In the near future, the driver core is going to not allow direct access
to the driver_data pointer in struct device.  Instead, the functions
dev_get_drvdata() and dev_set_drvdata() should be used.  These functions
have been around since the beginning, so are backwards compatible with
all older kernel versions.

Cc: Samuel Ortiz <sameo@linux.intel.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/mfd/wm8400-core.c b/drivers/mfd/wm8400-core.c
index cf30d06..7c21bf7 100644
--- a/drivers/mfd/wm8400-core.c
+++ b/drivers/mfd/wm8400-core.c
@@ -265,7 +265,7 @@
 
 	mutex_init(&wm8400->io_lock);
 
-	wm8400->dev->driver_data = wm8400;
+	dev_set_drvdata(wm8400->dev, wm8400);
 
 	/* Check that this is actually a WM8400 */
 	ret = wm8400->read_dev(wm8400->io_data, WM8400_RESET_ID, 1, &reg);