drm/i915: Convert vm->dev backpointer to vm->i915

99% of the time we access i915_address_space->dev we want the i915
device and not the drm device, so let's store the drm_i915_private
backpointer instead. The only real complication here are the inlines
in i915_vma.h where drm_i915_private is not yet defined and so we have
to choose an alternate path for our asserts.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161129095008.32622-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 0463655..3b9e60a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4228,9 +4228,8 @@ static void ironlake_fdi_disable(struct drm_crtc *crtc)
 	udelay(100);
 }
 
-bool intel_has_pending_fb_unpin(struct drm_device *dev)
+bool intel_has_pending_fb_unpin(struct drm_i915_private *dev_priv)
 {
-	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct intel_crtc *crtc;
 
 	/* Note that we don't need to be called with mode_config.lock here
@@ -4240,7 +4239,7 @@ bool intel_has_pending_fb_unpin(struct drm_device *dev)
 	 * cannot claim and pin a new fb without at least acquring the
 	 * struct_mutex and so serialising with us.
 	 */
-	for_each_intel_crtc(dev, crtc) {
+	for_each_intel_crtc(&dev_priv->drm, crtc) {
 		if (atomic_read(&crtc->unpin_work_count) == 0)
 			continue;