i965/blorp: Instruct vertex fetcher to provide prim instance id

This will indicate target layer (Render Target Array Index) needed
for layered clears.

v2: Use 3DSTATE_VF_SGVS for gen8+

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
1 file changed