drm/i915: Refer to GGTT {,VM} consistently

Refer to the GGTT VM consistently as "ggtt->base" instead of just "ggtt",
"vm" or indirectly through other variables like "dev_priv->ggtt.base"
to avoid confusion with the i915_ggtt object itself and PPGTT VMs.

Refer to the GGTT as "ggtt" instead of indirectly through chaining.

As a bonus gets rid of the long-standing i915_obj_to_ggtt vs.
i915_gem_obj_to_ggtt conflict, due to removal of i915_obj_to_ggtt!

v2:
- Added some more after grepping sources with Chris

v3:
- Refer to GGTT VM through ggtt->base consistently instead of ggtt_vm
  (Chris)

v4:
- Convert all dev_priv->ggtt->foo accesses to ggtt->foo.

v5:
- Make patch checker happy

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 60bb486..e6b5ee5 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2444,6 +2444,7 @@
 {
 	struct drm_device *dev = crtc->base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct i915_ggtt *ggtt = &dev_priv->ggtt;
 	struct drm_i915_gem_object *obj = NULL;
 	struct drm_mode_fb_cmd2 mode_cmd = { 0 };
 	struct drm_framebuffer *fb = &plane_config->fb->base;
@@ -2459,7 +2460,7 @@
 	/* If the FB is too big, just don't use it since fbdev is not very
 	 * important and we should probably use that space with FBC or other
 	 * features. */
-	if (size_aligned * 2 > dev_priv->ggtt.stolen_usable_size)
+	if (size_aligned * 2 > ggtt->stolen_usable_size)
 		return false;
 
 	mutex_lock(&dev->struct_mutex);
@@ -15282,7 +15283,8 @@
 
 void intel_modeset_init(struct drm_device *dev)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct i915_ggtt *ggtt = &dev_priv->ggtt;
 	int sprite, ret;
 	enum pipe pipe;
 	struct intel_crtc *crtc;
@@ -15346,7 +15348,7 @@
 		dev->mode_config.cursor_height = MAX_CURSOR_HEIGHT;
 	}
 
-	dev->mode_config.fb_base = dev_priv->ggtt.mappable_base;
+	dev->mode_config.fb_base = ggtt->mappable_base;
 
 	DRM_DEBUG_KMS("%d display pipe%s available.\n",
 		      INTEL_INFO(dev)->num_pipes,