Merge tag 'topic/struct_mutex-2016-04-21' of git://anongit.freedesktop.org/drm-intel into drm-next

struct_mutex cleanups and error paths fixes. Unfortunately I didn't manage
to get acks from everyone, but this stuff has been hanging out for months
now and imo simple enough to just land the remaining few patches. But
separate pull request so that you can take a look yourself.

* tag 'topic/struct_mutex-2016-04-21' of git://anongit.freedesktop.org/drm-intel:
  drm/vma_manage: Drop has_offset
  drm/vgem: Drop dev->struct_mutex
  drm/vgem: Move get_pages to gem_create
  drm/vgem: Simplify dumb_map
  drm/exynos: drop struct_mutex from fbdev setup
  drm/exynos: drop struct_mutex from exynos_drm_gem_get_ioctl
  drm/exynos: drop struct_mutex from exynos_gem_map_sgt_with_dma
  drm/exynos: Drop dev->struct_mutex from mmap offset function
  drm/nouveau: Drop dev->struct_mutex from fbdev init
  drm/qxl: Use unlocked gem unreferencing
  drm/omapdrm: Use unlocked gem unreferencing
  drm/nouveau: Use unlocked gem unreferencing