virgl: Set use_staging in resource_from_handle

This flag controls virgl's behavior when buffers are accessed on the guest through Mesa's GBM interface.

As such, the flag needs to be consistent in both the resource creation and fd-import case. Previously, the fd-import resource's flag value would be inconsistent with the original resource's value.

This patch fixes this by inferring the value of this flag based on the resources size.

Signed-Off By: Isaac Bosompem mrisaacb@google.com

/cc @olv