Merge branch 'drm-next-3.18' of git://people.freedesktop.org/~agd5f/linux into drm-next

concurrent buffer reads.

* 'drm-next-3.18' of git://people.freedesktop.org/~agd5f/linux:
  drm/radeon: allow concurrent buffer reads
  drm/radeon: add the infrastructure for concurrent buffer access
  drm/ttm: allow fence to be added as shared