drm: kill ->gem_init_object() and friends

drm: kill ->gem_init_object() and friends

All drivers embed gem-objects into their own buffer objects. There is no
reason to keep drm_gem_object_alloc(), gem->driver_private and
->gem_init_object() anymore.

New drivers are highly encouraged to do the same. There is no benefit in
allocating gem-objects separately.

Cc: Dave Airlie <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Rob Clark <[email protected]>
Cc: Inki Dae <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Patrik Jakobsson <[email protected]>
Signed-off-by: David Herrmann <[email protected]>
Acked-by: Alex Deucher <[email protected]>
Signed-off-by: Dave Airlie <[email protected]>