drm/i915: remove intel_vgpu_gtt::active_ppgtt_mm_bitmap

intel_vgpu_gtt::active_ppgtt_mm_bitmap was never used since its
addition in commit 2707e444 (drm/i915/gvt: vGPU graphics memory
virtualization). Drop it.

Found by https://github.com/jirislaby/clang-struct.
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240216065326.6910-12-jirislaby@kernel.org

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

@@ -208,7 +208,6 @@ struct intel_vgpu_scratch_pt {
 
 struct intel_vgpu_gtt {
 	struct intel_vgpu_mm *ggtt_mm;
-	unsigned long active_ppgtt_mm_bitmap;
 	struct list_head ppgtt_mm_list_head;
 	struct radix_tree_root spt_tree;
 	struct list_head oos_page_list_head;