drm/bochs: use drm_gem_vram_offset to get bo offset v2

Switch over to GEM VRAM's implementation to retrieve bo->offset.
Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/372931/

drivers/gpu/drm/bochs/bochs_kms.c

@@ -29,16 +29,21 @@ static void bochs_plane_update(struct bochs_device *bochs,
 			       struct drm_plane_state *state)
 {
 	struct drm_gem_vram_object *gbo;
+	s64 gpu_addr;
 
 	if (!state->fb || !bochs->stride)
 		return;
 
 	gbo = drm_gem_vram_of_gem(state->fb->obj[0]);
+	gpu_addr = drm_gem_vram_offset(gbo);
+	if (WARN_ON_ONCE(gpu_addr < 0))
+		return; /* Bug: we didn't pin the BO to VRAM in prepare_fb. */
+
 	bochs_hw_setbase(bochs,
 			 state->crtc_x,
 			 state->crtc_y,
 			 state->fb->pitches[0],
-			 state->fb->offsets[0] + gbo->bo.offset);
+			 state->fb->offsets[0] + gpu_addr);
 	bochs_hw_setformat(bochs, state->fb->format);
 }