drm/gem: convert to new unified vma manager

Use the new vma manager instead of the old hashtable. Also convert all
drivers to use the new convenience helpers. This drops all the
(map_list.hash.key << PAGE_SHIFT) non-sense.

Locking and access-management is exactly the same as before with an
additional lock inside of the vma-manager, which strictly wouldn't be
needed for gem.

v2:
 - rebase on drm-next
 - init nodes via drm_vma_node_reset() in drm_gem.c
v3:
 - fix tegra
v4:
 - remove duplicate if (drm_vma_node_has_offset()) checks
 - inline now trivial drm_vma_node_offset_addr() calls
v5:
 - skip node-reset on gem-init due to kzalloc()
 - do not allow mapping gem-objects with offsets (backwards compat)
 - remove unneccessary casts

Cc: Inki Dae <inki.dae@samsung.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@gmail.com>