virgl: quadruple command buffer size
Tested running WebGL aquarium on Nvidia host (10,000 fishes) This moves us from 7 fps to 9 fps. After quadrupling, performance gains diminish. v2: Remove change ID (Erik) Tested-By:Gert Wollny <gert.wollny@collabora.com> Reviewed-by:
Erik Faye-Lund <erik.faye-lund@collabora.com> (cherry picked from commit c0773315)