USB: Fix oops in PhidgetServo

The PhidgetServo causes an Oops when any of its sysfs attributes are read
or written too, making the driver useless.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/misc/phidgetservo.c b/drivers/usb/misc/phidgetservo.c
index 7163f05..0d9de2f 100644
--- a/drivers/usb/misc/phidgetservo.c
+++ b/drivers/usb/misc/phidgetservo.c
@@ -282,6 +282,7 @@
 		dev->dev = NULL;
 		goto out;
 	}
+	dev_set_drvdata(dev->dev, dev);
 
 	servo_count = dev->type & SERVO_COUNT_QUAD ? 4 : 1;