drm/i915/gvt: remove unused to_gvt() and reduce includes

gvt.h has no need to include i915_drv.h once the unused to_gvt() has
been removed.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230926121904.499888-1-jani.nikula@intel.com

Author: jnikula

drivers/gpu/drm/i915/gvt/gvt.h

@@ -39,7 +39,7 @@
 
 #include <asm/kvm_page_track.h>
 
-#include "i915_drv.h"
+#include "gt/intel_gt.h"
 #include "intel_gvt.h"
 
 #include "debug.h"
@@ -368,11 +368,6 @@ struct intel_gvt {
 	struct dentry *debugfs_root;
 };
 
-static inline struct intel_gvt *to_gvt(struct drm_i915_private *i915)
-{
-	return i915->gvt;
-}
-
 enum {
 	/* Scheduling trigger by timer */
 	INTEL_GVT_REQUEST_SCHED = 0,