- 'dev' in struct hid_device changed from struct usb_device to
struct device and fixed all the users
- renamed functions which are part of USB HID API from 'hid_*' to
'usbhid_*'
- force feedback initialization moved from common part into USB-specific
driver
- added usbhid.h header for USB HID API users
- removed USB-specific fields from struct hid_device and moved them
to new usbhid_device, which is pointed to by hid_device->driver_data
- fixed all USB users to use this new structure