sound: use dev_set_drvdata

Eliminate direct accesses to the driver_data field.
cf 82ab13b26f15f49be45f15ccc96bfa0b81dfd015

The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
struct device *dev;
expression E;
type T;
@@

- dev->driver_data = (T)E
+ dev_set_drvdata(dev, E)

@@
struct device *dev;
type T;
@@

- (T)dev->driver_data
+ dev_get_drvdata(dev)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>