driver core: dev_set_drvdata returns void

dev_set_drvdata can no longer fail, so it could return void.

All callers have hopefully been updated to no longer check for the
return value.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>