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/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 820c91f5..d3ebb2f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3154,9 +3154,6 @@
 bool i915_gem_obj_is_pinned(struct drm_i915_gem_object *obj);
 
 /* Some GGTT VM helpers */
-#define i915_obj_to_ggtt(obj) \
-	(&((struct drm_i915_private *)(obj)->base.dev->dev_private)->ggtt.base)
-
 static inline struct i915_hw_ppgtt *
 i915_vm_to_ppgtt(struct i915_address_space *vm)
 {
@@ -3173,7 +3170,10 @@
 static inline unsigned long
 i915_gem_obj_ggtt_size(struct drm_i915_gem_object *obj)
 {
-	return i915_gem_obj_size(obj, i915_obj_to_ggtt(obj));
+	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
+	struct i915_ggtt *ggtt = &dev_priv->ggtt;
+
+	return i915_gem_obj_size(obj, &ggtt->base);
 }
 
 static inline int __must_check
@@ -3181,7 +3181,10 @@
 		      uint32_t alignment,
 		      unsigned flags)
 {
-	return i915_gem_object_pin(obj, i915_obj_to_ggtt(obj),
+	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
+	struct i915_ggtt *ggtt = &dev_priv->ggtt;
+
+	return i915_gem_object_pin(obj, &ggtt->base,
 				   alignment, flags | PIN_GLOBAL);
 }