Pull up following revision(s) (requested by riastradh in ticket #1003):

sys/external/bsd/drm2/dist/drm/i915/intel_sdvo.c: revision 1.8
sys/external/bsd/drm2/dist/drm/ttm/ttm_tt.c: revision 1.10
sys/external/bsd/drm2/drm/drm_scatter.c: revision 1.4
sys/external/bsd/drm2/dist/drm/i915/i915_reg.h: revision 1.2
sys/external/bsd/drm2/linux/linux_ww_mutex.c: revision 1.3
sys/external/bsd/drm2/linux/linux_ww_mutex.c: revision 1.4
sys/external/bsd/drm2/linux/linux_idr.c: revision 1.6

Pull in upstream commit:
Author: Ville Syrj=E4l=E4 <ville.syrjala%linux.intel.com@localhost>
Date:  Mon Jun 9 16:20:46 2014 +0300
    drm/i915: Avoid div-by-zero when pixel_multiplier is zero
On certain platforms pixel_multiplier is read out in
.get_pipe_config(), but it also gets used to calculate the
pixel clock in intel_sdvo_get_config(). If the pipe is disabled
but some SDVO outputs are active, we may end up dividing by zero
in intel_sdvo_get_config().
Fixes https://bugs.freedesktop.org/show_bug.cgi?id=3D76520
Tweak slightly sketchy logic in linux_idr.
1. idr_preload can fail if you don't set __GFP_WAIT.
2. If idr_preload fails, it is wrong for idr_alloc to assert.
3. There is no way for idr_alloc to know what flags idr_preload got.
Probably won't *fix* any bugs, but if there is a bug with a missing
__GFP_WAIT, then we will learn about a trifle sooner.
Fix error branch in ttm_dma_tt_init to avoid double-free.
Should fix symptom of PR kern/52438, but who knows what underlying
problem causes us to reach the error branch in the first place.
Fix lockdebug_locked annotations.
When thread A grants ownership to thread B waiting with a context,
thread B needs to assert lockdebug_locked; otherwise, when it
releases, lockdebug_unlocked thinks it's releasing an unlocked
ww_mutex.

Fixes LOCKDEBUG failure with radeon noticed by martin@.

more const

XXX: add a NULL init to avoid a GCC 6 maybe uninit warning.

Remove UB from definition of symbols in i915_reg.h
Kernel Undefined Behavior Sanitizer enforces more warnings in build time.
This makes the build fatal in the drm/i915 code in:
- intel_ddi_put_crtc_pll(),
- intel_ddi_clock_get(),
- intel_ddi_pll_enable(),
- intel_ddi_setup_hw_pll_state().
The error message in all the cases says:
  error: case label does not reduce to an integer constant
Set the type of the value left shifted to unsigned.
This change is required to build NetBSD/amd64 with KUBSan.

(martin)