i915: add dma-buf vmap support for exporting vmapped buffer

This is used to export a vmapping to the udl driver so that
i915 and udl can share the udl scanout.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 377c21f..c9cfc67 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -942,6 +942,9 @@
 
 	/* prime dma-buf support */
 	struct sg_table *sg_table;
+	void *dma_buf_vmapping;
+	int vmapping_count;
+
 	/**
 	 * Used for performing relocations during execbuffer insertion.
 	 */