radv: set the maximum number of IBs per submit to 192

This fixes random SteamVR corruption, see
https://github.com/ValveSoftware/SteamVR-for-Linux/issues/181



Fixes: 4d30f2c6 ("radv/winsys: remove the max IBs per submit limit for the fallback path")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit ae77f123)