drm/i915/gvt: clean up intel_gvt.h as interface for i915 core

i915 core should only call functions and structures exposed through
intel_gvt.h. Remove internal gvt.h and i915_pvinfo.h.

Change for internal intel_gvt structure as private handler which
not requires to expose gvt internal structure for i915 core.

v2: Fix per Chris's comment
- carefully handle dev_priv->gvt assignment
- add necessary bracket for macro helper
- forward declartion struct intel_gvt
- keep free operation within same file handling alloc

v3: fix use after free and remove intel_gvt.initialized

v4: change to_gvt() to an inline

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4d1133f..5024ad9 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1778,7 +1778,7 @@
 
 	struct i915_virtual_gpu vgpu;
 
-	struct intel_gvt gvt;
+	struct intel_gvt *gvt;
 
 	struct intel_guc guc;
 
@@ -2992,7 +2992,7 @@
 
 static inline bool intel_gvt_active(struct drm_i915_private *dev_priv)
 {
-	return dev_priv->gvt.initialized;
+	return dev_priv->gvt;
 }
 
 static inline bool intel_vgpu_active(struct drm_i915_private *dev_priv)