Bring some drm module changes over from the XFree86 trunk:

Bring some drm module changes over from the XFree86 trunk:
- Reset 'bound' flag for an agp entry after undbind succeeded in
    drm_agpsupport.h (Egbert Eich).
- Ignore hw_lock for drm device if lock was set by a different instance (ie
    Xserver) to prevent second server from spinning in driver release
    function (currently only relevant for i8xx drm drivers) (David Dawes).
- Use the agpgart "key" for the unique handle for bindings rather than the
    memory address (the key is guaranteed to be unique) (David Dawes).