r600g: drop use_mem_constant.

since we plan on using dx10 constant buffers everywhere.

src/gallium/drivers/r600/r600_shader.h

@@ -43,7 +43,6 @@ struct r600_shader {
 	struct r600_shader_io	output[32];
 	enum radeon_family	family;
 	boolean			uses_kill;
-	boolean			use_mem_constant;
 };
 
 int r600_shader_from_tgsi(const struct tgsi_token *tokens, struct r600_shader *shader);