gallium/tgsi: add missing #include

Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

src/gallium/auxiliary/tgsi/tgsi_util.h

@@ -32,6 +32,8 @@
 extern "C" {
 #endif
 
+#include "pipe/p_shader_tokens.h"
+
 struct tgsi_src_register;
 struct tgsi_full_src_register;
 struct tgsi_full_instruction;