radeon userptr support.

* 'drm-next-3.18' of git://people.freedesktop.org/~agd5f/linux:
  drm/radeon: allow userptr write access under certain conditions
  drm/radeon: add userptr flag to register MMU notifier v3
  drm/radeon: add userptr flag to directly validate the BO to GTT
  drm/radeon: add userptr flag to limit it to anonymous memory v2
  drm/radeon: add userptr support v8

Conflicts:
	drivers/gpu/drm/radeon/radeon_prime.c