driconf: Advertise GL_EXT_shader_image_load_store on iris for SVP13
driconf: Advertise GL_EXT_shader_image_load_store on iris for SVP13
SPECviewperf creo-03 needs GL_EXT_shader_image_load_store in order for its shaders to compile but we don't support a few corner cases that didn't make it into the ARB variant. It seems to run fine with an override, so just do that for now.