minigbm: virtgpu/cross_domain: update protocol

- Update to match latest CONTEXT_INIT proposal
- Update cross domain protocol to match crosvm
  (crrev.com/c/3055850) & Sommelier (crrev.com/c/3054321)

BUG=b:173630595
TEST=local testing with cross domain backend

Change-Id: I7420b03988bc8aed5b2bc53a0c54498a9ee47f86
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/3119670
Reviewed-by: Jason Macnak <natsu@google.com>
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
diff --git a/drv_priv.h b/drv_priv.h
index c720077..63c69b4 100644
--- a/drv_priv.h
+++ b/drv_priv.h
@@ -34,7 +34,7 @@
 	 * specific metadata.  It's easiest just to stuff all the metadata here rather than
 	 * having two metadata structs.
 	 */
-	uint64_t blob_id;
+	uint32_t blob_id;
 	uint32_t map_info;
 	int32_t memory_idx;
 	int32_t physical_device_idx;