i965: Upload state on primitive switch, don't just prepare it.

This was a regression in 59b2c2adbb that broke
blender, among other apps.

src/mesa/drivers/dri/i965/brw_draw.c

@@ -105,6 +105,7 @@ static GLuint brw_set_prim(struct brw_context *brw, GLenum prim)
       }
 
       brw_validate_state(brw);
+      brw_upload_state(brw);
    }
 
    return hw_prim[prim];