mesa/st: Pad out _mesa_sysval_to_semantic for new SYSTEM_VALUE_* enums

GL_ARB_shader_draw_parameters added two new system values.  This gets us
back to mapping mesa system values to the right TGSI semantics.

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -4328,6 +4328,8 @@ const unsigned _mesa_sysval_to_semantic[SYSTEM_VALUE_MAX] = {
    TGSI_SEMANTIC_INSTANCEID,
    TGSI_SEMANTIC_VERTEXID_NOBASE,
    TGSI_SEMANTIC_BASEVERTEX,
+   0, /* SYSTEM_VALUE_BASE_INSTANCE */
+   0, /* SYSTEM_VALUE_DRAW_ID */
 
    /* Geometry shader
     */